[mlir] Width parameterization of BitEnum attributes

This diff contains:

- Parameterization of bit enum attributes in OpBase.td by bit width (e.g. 32
and 64). Previously, all enums were 32-bits. This brings enum functionality in
line with other integer attributes, and allows for bit enums greater than 32
bits.
- SPIRV and Vector dialects were updated to use bit enum attributes with an
  explicit bit width

Reviewed By: mehdi_amini

Differential Revision: https://reviews.llvm.org/D123095