[clang] [llvm] [mlir] [polly] [NFC] Rename `Intrinsic::getDeclaration` to `getOrInsertDeclaration` (PR #111752)

[Daniel Chen via cfe-commits]

DanielCChen wrote:

> > > `test_demangle` should definitely **not** be updated when renaming functions.
> > 
> > 
> > Could you please explain a bit more since this is new to me? Thanks in advance!
> 
> The use of LLVM symbols in this file is incidental -- it's just a data set of mangled C++ symbol names. The file should only change if the mangling implementation changes.

OK. I see. Yeah, makes senses now as it reduces maintenance cost. Thanks for the explanation. 

https://github.com/llvm/llvm-project/pull/111752