This PR is quite similiar to
https://github.com/llvm/llvm-project/pull/182805.
We added basic support of attribute definitions in Python-defined
dialects, including:
- IRDL codegen for attribute definitions
- Attr builders like `MyAttr.get(..)` and attr parameter accessors (e.g.
`my_attr.param1`)
- Use Python-defined attrs in Python-defined operations
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