Cherry-pick of #83128, #82399, and #82878, merged as ea6ca2b5db, 0c4e56174b, and e34eb3331f respectively.
**Explanation**: Currently `test/CMakeLists.txt` can only set `SWIFT_LIT_ARGS` for all tests uniformly. This means that we can't have tests for Embedded Swift with a different set of `lit.py` arguments.
Also, create new `check-swift-embedded-wasi` target from `test/CMakeLists.txt`, tweak `lit.cfg` to support WASI Clang resource dir, exclude unsupported tests based on `CPU=wasm32` instead of `OS=wasi`.
**Scope**: Limited to Embedded Swift test suite.
**Risk**: Low, due to limited scope.
**Testing**: #82878 was incubated on `main` for 2 weeks, #82399 for 3 weeks with no disruption, #83128 merged this week, but enables all these tests on CI, which are consistently passing.
**Issue**: rdar://156585717
**Reviewer**: @bnbarham
Certain traps can't be supported on WASI, such as expectations for crashes, `setjmp` use, dynamic linking, multi-threading etc. These tests are marked as `UNSUPPORTED` when targeting Wasm/WASI.
Because of the way grapheme breaking changes across updates to ICU and the Unicode standard, it may not even be legit to check this at all. It's certainly not unsafe to skip the check, so let's see if we can do that in release builds, as grapheme breaking is expensive.
This decreases total testing time by over a minute on my old Mac Pro.
It probably has much less effect on systems with fewer cores, but shouldn't
be any worse there.
Swift SVN r22745
