fix(clang-cl): reduce warnings

[Nerixyz]

When compiling with clang-cl, there are warnings not present with MSVC

• /MP isn't a thing in clang-cl.
• /W4 enables -Wunused-parameter in clang-cl (or this might be enabled by default) - either way, it's not enabled in MSVC and generates some warnings here.
• getRawUnqualified returned a std::string_view to a temporary std::string and clang warned about it.
• -Wself-move was ignored when __GNUC__ was defined. This isn't defined with clang-cl, so ignore it in the clang block.

[cppalliance-bot]

An automated preview of the documentation is available at https://900.mrdocs.prtest2.cppalliance.org/index.html

[cppalliance-bot]

An automated preview of the documentation is available at https://900.mrdocs.prtest2.cppalliance.org/index.html