[mlir] Quality of life improvements to python API types. (#66723)

* Moves several orphaned methods from Operation/OpView -> _OperationBase
so that both hierarchies share them (whether unknown or known to ODS).
* Adds typing information for missing `MLIRError` exception.
* Adds `DiagnosticInfo` typing.
* Adds `DenseResourceElementsAttr` typing that was missing.