Rollup merge of rust-lang#70988 - LeSeulArtichaut:triagebot-prioritize, r=Mark-Simulacrum

Setup the `@rustbot prioritize` command

See rust-lang/triagebot#453

r? @Mark-Simulacrum can you confirm that the `t-compiler/wg-prioritization` stream ID is `227806`?
cc @spastorino

Author: Centril

triagebot.toml

@@ -33,3 +33,7 @@ Thanks! <3
 [instructions]: https://rustc-dev-guide.rust-lang.org/ice-breaker/cleanup-crew.html
 """
 label = "ICEBreaker-Cleanup-Crew"
+
+[prioritize]
+label = "I-prioritize"
+zulip_stream = 227806