[Frontend] Rename NonIsolatedAsyncInheritsIsolationFromContext feature and add a feature for @execution

[xedin]

• NonIsolatedAsyncInheritsIsolationFromContext -> AsyncCallerExecution
• Hide @execution attribute behind an experimental feature ExecutionAttribute

[xedin]

@swift-ci please test

[xedin]

@swift-ci please test

[xedin]

@swift-ci please test

[xwu]

Can we hold off on renaming the experimental feature flag in the middle of the proposal review period (imminently starting) as we would want users to be able to try it out using the instructions they're given.

[hborla]

Can we hold off on renaming the experimental feature flag in the middle of the proposal review period (imminently starting) as we would want users to be able to try it out using the instructions they're given.

I asked for this change to be made specifically for the review so that there are two separate flags for 1. the additive features and 2. the default change. We should just build a toolchain on this PR.

[hborla]

@swift-ci please build toolchain

[hborla]

@xwu I think it's fine to kick off the review and note that the toolchain will come today - I'll update the thread with the toolchain and the flags once it's built

[xedin]

@swift-ci please build toolchain Windows platform

[xedin]

Toolchains:

• Ubuntu: https://download.swift.org/tmp/pull-request/79508/1273/ubuntu2004/PR-ubuntu2004.tar.gz
• macOS: https://ci.swift.org/job/swift-PR-toolchain-macos/1789/artifact/branch-main/swift-PR-79508-1789-osx.tar.gz
• Windows: https://ci-external.swift.org/job/swift-PR-build-toolchain-windows/5725/artifact/build/artifacts/

[xedin]

Windows toolchain is failing with an unrelated error:

TestFoundation/TestNSData.swift:466: error: TestNSData.test_base64EncodeDoesNotAddLineSeparatorsWhenStringFitsInLine : XCTAssertEqual failed: ("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA


") is not equal to ("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA") - each 3 byte is converted into 4 characterss. 48 / 3 * 4 <= 64, therefore result should not have line separator.

TestFoundation/TestNSData.swift:472: error: TestNSData.test_base64EncodeDoesNotAddLineSeparatorsWhenStringFitsInLine : XCTAssertEqual failed: ("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA


") is not equal to ("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA") - each 3 byte is converted into 4 characterss. 57 / 3 * 4 <= 76, therefore result should not have line separator.

[xedin]

@swift-ci please build toolchain windows