Since LayoutPrespecialization has been enabled by default in all compiler
invocations for quite some time, it doesn't make sense for it to be treated as
experimental feature. Make it a baseline feature and remove all the
checks for it from the compiler.
Find all the usages of `--enable-experimental-feature` or
`--enable-upcoming-feature` in the tests and replace some of the
`REQUIRES: asserts` to use `REQUIRES: swift-feature-Foo` instead, which
should correctly apply to depending on the asserts/noasserts mode of the
toolchain for each feature.
Remove some comments that talked about enabling asserts since they don't
apply anymore (but I might had miss some).
All this was done with an automated script, so some formatting weirdness
might happen, but I hope I fixed most of those.
There might be some tests that were `REQUIRES: asserts` that might run
in `noasserts` toolchains now. This will normally be because their
feature went from experimental to upcoming/base and the tests were not
updated.
Since these features are experimental features, they can't be catagorized as
"baseline" features. However, there is no need to guard code in swiftinterfaces
that potentially uses syntax related to these features since all supported
compilers can parse the syntax.
* [ModuleInterface] Guard layout based prespecializations in swiftinterface files
rdar://107269447
To allow compilers that don't have this feature enabled to parse interface files that contain declarations that use layout based prespecializations, it has to be guarded.
* Incorporate feedback
