[mlir][NFC] Update dialect/op documentation to be consistent

Summary:
This revision performs a lot of different cleanups on operation documentation to ensure that they are consistent, e.g. using mlir code blocks, formatting, etc.

This revision also includes the auto-generated documentation into the hand-written documentation for the dialects that have a specific top-level dialect file. This updates the documentation for all dialects aside from SPIRV and STD. These dialects will be updated in a followup.

Differential Revision: https://reviews.llvm.org/D76734