github-actions: pin actions to commit SHAs and fix zizmor security findings#2432

Dorcas-BD wants to merge 1 commit intorust-lang:masterrust-lang/rustc-perf:masterfrom

Dorcas-BD:fix/zizmor-non-behavior-changesDorcas-BD/rustc-perf:fix/zizmor-non-behavior-changesCopy head branch name to clipboard