HLSL: Add 'f' suffix to float literals in code generation (#6381)

* HLSL: Add 'f' suffix to float literals in code generation

Fixes #6078

1) Previously, Slang would emit HLSL float literals without a suffix (e.g.,"1.5"),
which caused DXC to interpret them as 64-bit doubles by default unless
the -HV 202x flag was used. This could cause validation errors when these literals
were used with intrinsics that only accept 32-bit floats (like ddx, ddy).

This change modifies the HLSL emitter to explicitly add 'f' suffix to
32-bit float literals, ensuring they are correctly typed regardless of DXC's version or flags.
For example:
- "1.5" becomes "1.5f"
- "(0.0 / 0.0)" becomes "(0.0f / 0.0f)" for NaN
- "float4(1.0, 2.0, 3.0, 4.0)" becomes "float4(1.0f, 2.0f, 3.0f, 4.0f)"

2) Added a test case to verify the behavior with various float literal scenarios
including basic literals, intrinsic calls, and vector construction.

3) Remove some tests that were marked as known failures

* Add dxil test as suggested by jkwak-work

0 files changed, 0 insertions, 0 deletions