Cleanup tests to be friendlier to modules

[StephanTLavavej]

While experimentally running tests/std with Standard Library Modules, I encountered unnecessary dependencies on macros and non-Standard code. Although we're a long way from routinely running module configurations in tests/std, I'd like to clean up what I've found so far.

• Avoid _Is_any_of_v. We can use is_same_v instead of this internal machinery, at minimal verbosity cost.
• Use numeric_limits instead of macros.
• Avoid ambiguity with std::integral, std::numbers, std::expected. After import std; using namespace std;, if test code has global-scope integral, numbers, and expected, mentioning them unqualified is ambiguous. (This is theoretically an issue for headers too, as any header is allowed to drag in any other header.)
• Avoid the <cinttypes> print macros. These are difficult to read in any event, and static_casts are probably less annoying.

[AlexGuteniev]

• Use numeric_limits instead of macros.

Think the reverse was deliberate for throughput. <limits> is relatively heavy.

[AlexGuteniev]

Ah, never mind, it is test code.

[StephanTLavavej]

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