Cleanups: Test options

[StephanTLavavej]

• Remove workarounds for VSO-1350252 "ASan libraries do not provide variants for each _ITERATOR_DEBUG_LEVEL", fixed in VS 2022 17.5.
  • @strega-nil-ms explained to me that ASan was using the STL internally, which caused IDL mix-and-match problems, with /fno-sanitize-address-vcasan-lib being the workaround. Now that ASan has stopped using the STL internally, we can drop this workaround option.
• Drop -Xclang before -Wno-deprecated-declarations and -Wno-self-assign.
  • At some point, this was necessary, although I never really understood why. (My vague understanding is that early on, clang-cl really insisted on taking only MSVC-compatible options, and needed -Xclang before any Clang-specific options.) This is clearly no longer necessary, and we can directly pass the Clang warning suppression options, as we're already doing for -Wno-unqualified-std-cast-call.
• We don't need /Zc:strictStrings in the universal options anymore.
  • This is implied by /permissive- (and therefore /std:c++20), so we have extensive coverage.

C:\Temp>type meow.cpp

#include <iostream>

int main() {
    char* ptr = "Goodbye, deprecated world!\n";
    std::cout << ptr;
}

C:\Temp>cl /EHsc /nologo /W4 meow.cpp && meow
meow.cpp
Goodbye, deprecated world!

C:\Temp>cl /EHsc /nologo /W4 /Zc:strictStrings meow.cpp && meow
meow.cpp
meow.cpp(4): error C2440: 'initializing': cannot convert from 'const char [28]' to 'char *'
meow.cpp(4): note: Conversion from string literal loses const qualifier (see /Zc:strictStrings)

C:\Temp>cl /EHsc /nologo /W4 /permissive- meow.cpp && meow
meow.cpp
meow.cpp(4): error C2440: 'initializing': cannot convert from 'const char [28]' to 'char *'
meow.cpp(4): note: Conversion from string literal loses const qualifier (see /Zc:strictStrings)

C:\Temp>cl /EHsc /nologo /W4 /std:c++20 meow.cpp && meow
meow.cpp
meow.cpp(4): error C2440: 'initializing': cannot convert from 'const char [28]' to 'char *'
meow.cpp(4): note: Conversion from string literal loses const qualifier (see /Zc:strictStrings)

[StephanTLavavej]

I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed.