[lldb][test] Skip tests for features unsupported on WebAssembly (#207102)
- TestReturnValue, TestTrivialABI: a WebAssembly return value lives on
the operand stack with no way to locate it at a step-out, so the
returned value can't be recovered.
- TestScriptedFrameProvider, TestFrameProviderThreadFilter: the inferior
is multithreaded C++, which wasip1 can't build (no threads, and
inferiors are compiled without exception support).
- TestThreadLocal: reading thread-locals works, but the test checks the
platform-specific error reported when TLS isn't initialized yet, which
WebAssembly doesn't have (already xfail/skip on other platforms).