[clang] [Clang] Bugfixes and improved support for `AttributedType`s in lambdas (PR #85325)

[via cfe-commits]

Sirraide wrote:

Seeing as there are now two places where we want to adjust function types but also preserve sugar, I’ve gone ahead and added a generic `adjustType()` function that handles all of the sugar and takes a `function_ref` to perform the actual adjustment. 

The intent here is that, in the future, functions like `getFunctionTypeWithExceptionSpec()` should be able to delegate most of the work to that function instead.

https://github.com/llvm/llvm-project/pull/85325