Fix and simplify the feature-test macro test

[StephanTLavavej]

• Drop extra spaces in #error messages.
• Mechanically simplify.
  • This test originally covered both the compiler and library feature-test macros, and was therefore extremely paranoid about checking the behavior of the preprocessor. We gave the compiler test coverage to the compiler team a long time ago, so we can simplify the library test coverage now. This commit is a 100% regex search-and-replace, from:

    #ifndef (__cpp_lib_\w+)
    #error \1 is not defined
    #elif \1 != (\d{6}L)
    #error \1 is not \2
    #else
    STATIC_ASSERT\(\1 == \2\);
    #endif

    to:

    #ifdef $1
    STATIC_ASSERT($1 == $2);
    #else
    #error $1 is not defined
    #endif

    except with \n between each line of the "from" and "to" (presented here on separate lines for clarity).
• Simplify __cpp_lib_chrono and __cpp_lib_shared_ptr_arrays.
  • These are always defined, but to varying values, so they use a slightly different pattern.
• Simplify __cpp_lib_shift.
  • This was trying to be extra helpful with a message saying "is OLD_VALUE when it should be NEW_VALUE", but that made the code verbose and unsystematic. This test is passing, so we don't need elaborate error messages in case of failure.
• Fix damaged __cpp_lib_containers_ranges test.
  • This would never have detected __cpp_lib_containers_ranges being defined outside of the relevant mode.
• Mechanically simplify again (100% regex).
  • From:

    #ifdef (__cpp_lib_\w+)
    (STATIC_ASSERT\(\1 == \d{6}L\);)
    #else
    #error \1 is not defined
    #endif

    to:

    $2
    

• Manually simplify __cpp_lib_chrono and __cpp_lib_shared_ptr_arrays again.
  • This removes all occurrences of "is not defined".
• Mechanically simplify yet again (100% regex).
  • From:

    #else
    #ifdef (__cpp_lib_\w+)
    #error \1 is defined
    #endif
    #endif

    to:

    #elif defined($1)
    #error $1 is defined
    #endif

• Manually simplify __cpp_lib_shared_timed_mutex.
  • Testing for non-/clr:pure mode allows this to follow the consistent pattern.
• Fix damaged __cpp_lib_is_layout_compatible and __cpp_lib_is_pointer_interconvertible tests.
  • These tests weren't doing anything for C++14/17 mode. Now they'll detect the macros being present when they shouldn't be.
• DROP SHOUTY COMMENT.

[CaseyCarter]

This is so much nicer - thanks!

[StephanTLavavej]

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