[llvm] [LV] Add early-exit-with-store tests (PR #140899)

[Graham Hunter via llvm-commits]

huntergr-arm wrote:

I left `@exit_conditions_combined_in_single_branch` in `early_exit_legality.ll`, since the point of the test is having two exit conditions for a single branch (which just happens to have a store in it; could be any operation producing a side effect).

https://github.com/llvm/llvm-project/pull/140899