[DirectX] Set Shader Flag DisableOptimizations (#126813)
- Set the shader flag `DisableOptimizations` based on `optnone`
attribute of shader entry functions.
- Add DXIL Metadata Analysis pass as pre-requisite for Shader Flags pass
to obtain entry function information collected therein.
- Named module metadata `dx.disable_optimizations` is intended to
indicate disabling optimizations (`-O0`) via commandline flag. However,
its intent is fulfilled by `optnone` attribute of shader entry functions as
implemented in a recent change, and thus not needed. Delete
generation of named metadata and corresponding test file
`disable_opt.ll`.
- Add tests to verify correctness of setting shader flag.
Closes #112263
