[mlir][TableGen] Add ability to mark builders etc. deprecated

[krzysz00]

It'd be nice to have some mechanism - maybe a bit deprecated = 0; in AttrOrTypeBuilder and OpBuilder that'd cause the tablegen code to emit a [[deprecated]] on the method in question, so that we can put up compiler warnings ahead of our intent to remove something

[llvmbot]

@llvm/issue-subscribers-mlir

Author: Krzysztof Drewniak (krzysz00)

It'd be nice to have some mechanism - maybe a `bit deprecated = 0;` in `AttrOrTypeBuilder` and `OpBuilder` that'd cause the tablegen code to emit a `[[deprecated]]` on the method in question, so that we can put up compiler warnings ahead of our intent to remove something