Rollup merge of rust-lang#86687 - JohnTitor:perf-regression-label, r=Mark-Simulacrum

Allow anyone to set `perf-regression` label

The main purpose is to allow the triage bot to set the label: rust-lang#86617 (comment)

r? `@Mark-Simulacrum`

Author: JohnTitor

triagebot.toml

@@ -4,6 +4,7 @@ allow-unauthenticated = [
     "D-*",
     "requires-nightly",
     "regression-*",
+    "perf-regression",
     # I-* without I-nominated
     "I-*", "!I-nominated",
     "AsyncAwait-OnDeck",