This pr removes the redundancy of having the same enums defined in both
the front-end and back-end of handling root signatures. Since there are
many more uses of the enum in the front-end of the code, we will adhere
to the naming conventions used in the front-end, to minimize the diff.
The macros in `DXContainerConstants.def` are also touched-up to be
consistent and to have each macro name follow its respective definition
in d3d12.h and searchable by name
[here](https://learn.microsoft.com/en-us/windows/win32/api/d3d12/).
Additionally, the many `getEnumNames` are moved to `DXContainer` from
`HLSLRootSignatureUtils` as they we will want them to be exposed
publicly anyways.
Changes for each enum follow the pattern of a commit that will make the
enum definition in `DXContainer` adhere to above listed naming
conventions, followed by a commit to actually use that enum in the
front-end.
Resolves https://github.com/llvm/llvm-project/issues/145815
0ceb0c377a