This PR relands #28672 on top of the flag removal and the test
demonstrating a breakage in Suspense for legacy mode.

React has deprecated module pattern Function Components for many years
at this point. Supporting this pattern required React to have a concept
of an indeterminate component so that when a component first renders it
can turn into either a ClassComponent or a FunctionComponent depending
on what it returns. While this feature was deprecated and put behind a
flag it is still in stable. This change remvoes the flag, removes the
warnings, and removes the concept of IndeterminateComponent from the
React codebase.

While removing IndeterminateComponent type Seb and I discovered that we
needed a concept of IncompleteFunctionComponent to support Suspense in
legacy mode. This new work tag is only needed as long as legacy mode is
around and ideally any code that considers this tag will be excludable
from OSS builds once we land extra gates using `disableLegacyMode` flag.

DiffTrain build for [5998a77](5998a77)

…#28657)

Saves some bytes and ensures that we're actually disabling it.

Turns out this flag wasn't disabling React Native/Fabric, React Noop and
React ART legacy modes so those are updated too.

Should be rebased on #28681.

…#28657)

Saves some bytes and ensures that we're actually disabling it.

Turns out this flag wasn't disabling React Native/Fabric, React Noop and
React ART legacy modes so those are updated too.

Should be rebased on #28681.

DiffTrain build for [5de8703](5de8703)

This PR relands facebook#28672 on top of the flag removal and the test
demonstrating a breakage in Suspense for legacy mode.

React has deprecated module pattern Function Components for many years
at this point. Supporting this pattern required React to have a concept
of an indeterminate component so that when a component first renders it
can turn into either a ClassComponent or a FunctionComponent depending
on what it returns. While this feature was deprecated and put behind a
flag it is still in stable. This change remvoes the flag, removes the
warnings, and removes the concept of IndeterminateComponent from the
React codebase.

While removing IndeterminateComponent type Seb and I discovered that we
needed a concept of IncompleteFunctionComponent to support Suspense in
legacy mode. This new work tag is only needed as long as legacy mode is
around and ideally any code that considers this tag will be excludable
from OSS builds once we land extra gates using `disableLegacyMode` flag.

…facebook#28657)

Saves some bytes and ensures that we're actually disabling it.

Turns out this flag wasn't disabling React Native/Fabric, React Noop and
React ART legacy modes so those are updated too.

Should be rebased on facebook#28681.

Full list of changes:
* Look for a ReactMemoCacheSentinel on state
([gsathya](https://github.com/gsathya) in
[#28831](#28831))
* Use use() in the Cache if available
([sebmarkbage](https://github.com/sebmarkbage) in
[#28793](#28793))
* feat[devtools-fusebox]: support theme option
([hoxyq](https://github.com/hoxyq) in
[#28832](#28832))
* feat[devtools]: add package for fusebox integration
([hoxyq](https://github.com/hoxyq) in
[#28553](#28553))
* feat[devtools]: add method for connecting backend with custom
messaging protocol ([hoxyq](https://github.com/hoxyq) in
[#28552](#28552))
* Rename SECRET INTERNALS to
`__CLIENT_INTERNALS_DO_NOT_USE_OR_WARN_USERS_THEY_CANNOT_UPGRADE`
([sebmarkbage](https://github.com/sebmarkbage) in
[#28789](#28789))
* Flatten ReactSharedInternals
([sebmarkbage](https://github.com/sebmarkbage) in
[#28783](#28783))
* feat[devtools]: ship source maps for content scripts and ignore list
installHook script ([hoxyq](https://github.com/hoxyq) in
[#28730](#28730))
* Track Owner for Server Components in DEV
([sebmarkbage](https://github.com/sebmarkbage) in
[#28753](#28753))
* Move ReactDOMLegacy implementation into RootFB
([sebmarkbage](https://github.com/sebmarkbage) in
[#28656](#28656))
* Reland #28672: Remove IndeterminateComponent
([gnoff](https://github.com/gnoff) in
[#28681](#28681))
* Remove reference to deleted <Cache> in un-linted file
([josephsavona](https://github.com/josephsavona) in
[#28715](#28715))
* [be] Remove unshipped experimental <Cache> element type
([josephsavona](https://github.com/josephsavona) in
[#28698](#28698))
* Revert "Remove module pattern function component support"
([rickhanlonii](https://github.com/rickhanlonii) in
[#28670](#28670))
* Remove module pattern function component support
([gnoff](https://github.com/gnoff) in
[#27742](#27742))
* [RTR] Enable warning flag ([jackpope](https://github.com/jackpope) in
[#28419](#28419))
* Update error messages ([rickhanlonii](https://github.com/rickhanlonii)
in [#28652](#28652))
* fix[devtools/ci]: split profiling cache test for different react
versions and toEqual checker ([hoxyq](https://github.com/hoxyq) in
[#28628](#28628))
* Guard against legacy context not being supported in DevTools fixture
([eps1lon](https://github.com/eps1lon) in
[#28596](#28596))
* Use `declare const` instead of `declare var`
([kassens](https://github.com/kassens) in
[#28599](#28599))
* Update isConcurrent RTR option usage
([jackpope](https://github.com/jackpope) in
[#28546](#28546))
* Disable legacy context ([kassens](https://github.com/kassens) in
[#27991](#27991))
* Remove invokeGuardedCallback and replay trick
([sebmarkbage](https://github.com/sebmarkbage) in
[#28515](#28515))
* Remove remaining usages of ReactTestUtils in tests unrelated to
`react-dom/test-util` ([eps1lon](https://github.com/eps1lon) in
[#28534](#28534))
* fix[devtools/e2e]: fixed source inspection in e2e tests
([hoxyq](https://github.com/hoxyq) in
[#28518](#28518))
* Devtools: Display actual pending state when inspecting `useTransition`
([eps1lon](https://github.com/eps1lon) in
[#28499](#28499))

This PR relands #28672 on top of the flag removal and the test
demonstrating a breakage in Suspense for legacy mode.

React has deprecated module pattern Function Components for many years
at this point. Supporting this pattern required React to have a concept
of an indeterminate component so that when a component first renders it
can turn into either a ClassComponent or a FunctionComponent depending
on what it returns. While this feature was deprecated and put behind a
flag it is still in stable. This change remvoes the flag, removes the
warnings, and removes the concept of IndeterminateComponent from the
React codebase.

While removing IndeterminateComponent type Seb and I discovered that we
needed a concept of IncompleteFunctionComponent to support Suspense in
legacy mode. This new work tag is only needed as long as legacy mode is
around and ideally any code that considers this tag will be excludable
from OSS builds once we land extra gates using `disableLegacyMode` flag.

DiffTrain build for commit 5998a77.

…#28657)

Saves some bytes and ensures that we're actually disabling it.

Turns out this flag wasn't disabling React Native/Fabric, React Noop and
React ART legacy modes so those are updated too.

Should be rebased on #28681.

DiffTrain build for commit 5de8703.