[mlir][spirv] Refresh base definitions to latest spec (v1.6)

This commit updates all SPIR-V enum definitions to match the latest
specification (v1.6 revision 2). Along the way, fixed some issues
in `gen_spirv_dialect.py` and added a new script for refreshing
all op definitions for such cases.

Reviewed By: kuhar

Differential Revision: https://reviews.llvm.org/D131293