[mlir-tblgen] Render enum keyword alternatives in generated attr/type docs
When mlir-tblgen generates documentation for AttrDefs/TypeDefs that have
EnumParameter fields, it previously rendered the raw C++ type (e.g.
`::mlir::ns::MyEnum`) in the syntax block. This was unhelpful for
users who need to know the valid keyword values.
This patch:
1. Adds an `EnumInfo enum = enumInfo;` field to the `EnumParameter`
TableGen class, persisting the enum record for tooling to inspect.
2. Modifies `emitAttrOrTypeDefAssemblyFormat` in OpDocGen.cpp to detect
EnumParameter fields and render their cases as backtick-quoted
alternatives (e.g. `` `read` | `read_write` ``).
3. Adds a test case to gen-dialect-doc.td verifying the new behavior.
Before:
#my_dialect.my_attr<
int32_t, # index
::mlir::ns::MyEnum, # access
>
After:
#my_dialect.my_attr<
int32_t, # index
`read` | `read_write`, # access
>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>