[clang] [KeyInstr][Clang] Coerced store atoms (PR #134653)

[Orlando Cazalet-Hyams via cfe-commits]

OCHyams wrote:

* Changed base to main (sorry to everyone automatically added as reviewer - I forgot to change to Draft PR before changing base).
* Removed Ret-atom checks (that PR hasn't been approved yet, want to land this one now it's approved).
* Fixed broken run lines (broken in bad rebase earlier).
* clang-formated

https://github.com/llvm/llvm-project/pull/134653