Update mlir GDB printers
Update prettyprinters.py to match MLIR changes.
This has gone unnoticed because no build bot is running tests with debug info.
I will look into what we can do about this separately. There is
https://green.lab.llvm.org/green/view/LLDB/job/lldb-cmake/,
from Apple. The Debug Info tests are failing despite the green result.
See https://github.com/llvm/llvm-project/issues/48872.
Note: the llvm-support.gdb test only works with Debug,
but not RelWithDebInfo because some checked symbols are stripped.
Reviewed By: dblaikie
Differential Revision: https://reviews.llvm.org/D116646