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.
Instead, use the `%target-swift-5.1-abi-triple` substitution to compile the tests
for deployment to the minimum OS versions required for use of _Concurrency APIs.
properties to require actor isolation.
Member initializer expressions are only used in a constructor with
matching actor isolation. If the isolation prohibits the member
initializer from being evaluated synchronously (or propagating required
isolation through closure bodies), then the default value cannot be used
and the member must be explicitly initialized in the constructor.
Member initializer expressions are also used as default arguments for the
memberwise initializer, and the same rules for default argument isolation
apply.
