Add FileCheck annotations to MIR-opt SROA tests

[JarlEvanson]

Part of #116971, adds FileCheck annotations to SROA MIR-opt tests in tests/mir-opt/sroa and a few uncategorized files.

r? cjgillot

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @cjgillot (or someone else) soon.

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[JarlEvanson]

Thanks for the review. I think I implemented all your suggestions, but let me know if I didn't.

[cjgillot]

Thanks! @bors r+ rollup

[bors]

:pushpin: Commit bae4f177b8767f6acab5474c6fec2734df759a32 has been approved by cjgillot

It is now in the queue for this repository.