perf: Reduce inner blocks tree depth (#50447)

* test: Await overlooked asynchronous task

The test helper executes asynchronous updates to the layout. If this is
not awaited, test failures can occur in certain circumstances.

* feat: Combine BlockList and BlockListCompact

Reduce code duplication between the separate components, e.g. item
render, footer, end-of-list block appender button, empty list
placeholder.

* wip: Gallery, Columns working; Buttons broken

Partially fix multi-column layouts by passing existing styles to a
wrapping view. All of the passed styles may not be necessary, need to
investigate. Also, Buttons render broken, wrapping lines and overflowing
the parent container.

* test: Fix nested lists tests

Nested lists now rely upon `BlockListItem`, which returns `null` if the
`blockWidth` has not yet been set. In order for test queries for nested
list items to succeed, we must trigger the `onLayout` callback for the
nested block lists. `BlockListItem` is now used to expand capabilities
for nested blocks, e.g. multi-column grid items.

* wip: Fix Blocks button layout

Fixes Buttons, but Columns remain broken.

* refactor: Remove unused BlockList title prop

* refactor: Separate inner block list styles

The list is no longer shared, so we can merely set the appropriate
styles on each list element.

* refactor: Remove unused virtualized listKey

Now that inner blocks do not use a virtualized list, a unique list key
is no longer necessary.

* refactor: Remove outdated inline comment

The scroll ref is no longer passed to inner blocks as they do not use
virtualized lists.

* wip: Explore nest Columns fixes

The relocated styles may need to be separate from the top-level block
list element, as the styles may conflict with other styles. It does not
fix Columns, however.

* Mobile - BlockList - Fix layout issues for stacked horizontally blocks

* fix: Revert Buttons alignment workaround

This caused issues for non-Buttons inner block alignment. The original
issue of Buttons inner blocks not rendering inline was addressed in
43c0b14918f8ed03037c01d94321922dc31a7fa3.

* fix: Column width sums less than 100% correct align

These styles caused columns to align to the center when their width sum
did not equal or execeed 100%. Removing these styles did not appear to
negatively impact other inner blocks or the use cases outlined in
#25621.

* refactor: Inner blocks use clientId key

This mirrors the approach for cells of top-level block lists. It is also
likely more robust, providing better performance when reordering blocks.

* refactor: Remove unnecessary key

The inner blocks list now sets a key on a wrapping view, rather than via
the `renderItem` function. Thus, this key is no superfluous.

* fix: Prevent block list footer from stretching to parent height

The parent flex styles were applied to the footer element. This wrapping
view prevents those styles from erroneously stretching the provided
footer element.

* Mobile - List block - Remove usage of useCompactList and disables the option to render the appender for InnerBlocks

* test: Update Android e2e Buttons block Xpath selector

This Xpath selector became outdated with the block list refactor.

* test: Delay query for block actions menu

Appium reported this cached element had been removed from the DOM.
Relocating the query seemingly resolved this issue.

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Co-authored-by: Gerardo <[email protected]>