[clang] [CIR][NFC] EHScope & Cleanups Iterators and operators overloading (PR #165317)

[Amr Hesham via cfe-commits]

AmrDeveloper wrote:

> This needs a test, which means it has to be introduced with (or after) something that mixes EH scopes with normal cleanups.

I just split this part from 165158, which already includes tests, just to make it easy to review

https://github.com/llvm/llvm-project/pull/165317