[clang] [Clang] Add default arguments to the parameter mapping (PR #192071)

[Oliver Hunt via cfe-commits]

https://github.com/ojhunt commented:

Looks reasonable to me, but I'm no deduction expert so I'll refrain from saying "looks good, go forth and land it" - I did have one minor question though

https://github.com/llvm/llvm-project/pull/192071