https://github.com/swiftlang/swift/pull/72612 can be reverted because it is no
longer necessary for the interface of the stdlib to be compatible with
compilers without `$TypedThrows` support.
I had to change the APIs to always be always emit into client instead of back
deployable since silgen_name seems to interfere with @backDeployment. So I
switched the implementation so that it instead uses an always emit into client
thunk with the in source function name and a usableFromInline function that has
the silgen_name. This ensures that we still appropriately export the same symbol
as we did before, so it is ABI stable.
This was approved as part of se-0414.
rdar://122030520
Since `withoutActuallyEscaping()` has adopted typed throws, it's no longer
visible to older compilers that do not support typed throws. We need to guard
use of the function in inlinable code to make sure the textual interface of
`_Concurrency` remains buildable with older compilers.
Resolves rdar://124352900
