.github/workflows: run CI and CodeQL in the merge queue

Signed-off-by: David Anderson <danderson@tailscale.com>

.github/workflows/codeql-analysis.yml

@@ -17,6 +17,7 @@ on:
   pull_request:
     # The branches below must be a subset of the branches above
     branches: [ main ]
+  merge_group:
   schedule:
     - cron: '31 14 * * 5'
 

.github/workflows/test.yml

@@ -24,6 +24,7 @@ on:
   pull_request:
     branches:
       - "*"
+  merge_group:
 
 concurrency:
   # For PRs, later CI runs preempt previous ones. e.g. a force push on a PR