[HLSL] Implement 202x conforming literals (#91015)

This implements the HLSL 202x conforming literals feature.

The feature proposal is available here:

https://github.com/microsoft/hlsl-specs/blob/main/proposals/0017-conforming-literals.md

The language specification for this behavior is available in (poorly
rendered) HTML or PDF:
https://microsoft.github.io/hlsl-specs/specs/hlsl.html#Lex.Literal.Float
https://microsoft.github.io/hlsl-specs/specs/hlsl.pdf

The main implementation details are:
1) Unsuffixed floating literals are `float`.
2) The integer `ll` suffix specifies `int64_t (aka long)` which is
64-bit because HLSL has no defined `long` keyword or `long long` type.

Resolves #85714