In this PR, we added basic support of type definitions in Python-defined
dialects, including:
- IRDL codegen for type definitions
- Type builders like `MyType.get(..)` and type parameter accessors (e.g.
`my_type.param1`)
- Use Python-defined types in Python-defined oeprations
```python
class TestType(Dialect, name="ext_type"):
pass
class Array(TestType.Type, name="array"):
elem_type: IntegerType[32] | IntegerType[64]
length: IntegerAttr
class MakeArrayOp(TestType.Operation, name="make_array"):
arr: Result[Array]
class MakeArray3Op(TestType.Operation, name="make_array3"):
arr: Result[Array[IntegerType[32], IntegerAttr[IntegerType[32], 3]]]
```
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