[clang] [llvm] [mlir] [TableGen] Add const variants of accessors for backend (PR #106658)

[Rahul Joshi via cfe-commits]

jurahul wrote:

Note, this is related to the following discourse thread that I had started: https://discourse.llvm.org/t/changing-tablegen-getallderiveddefinitions-to-return-arrayref-const-record/80586/5


https://github.com/llvm/llvm-project/pull/106658