GitHub: Special builds for more branches

Instead of triggering scan-build builds on pushes to the `scan-build` branch,
or valgrind builds on pushes to the `valgrind` branch, let's have pushes to
branches matching `scan-build*` and `valgrind*` branch name globs trigger the
corresponding builds.

Do not forget to delete those branches when you're done!

.github/workflows/scanbuild.yml

@@ -4,7 +4,7 @@ on:
     push:
       # Pushes to this branch get the scan-build treatment
       branches:
-         - 'scan-build'
+         - 'scan-build*'
 
     pull_request:
       # Changing this build gets it to run

.github/workflows/valgrind.yml

@@ -4,7 +4,7 @@ on:
     push:
       # Pushes to the valgrind branch get the valgrind treatment
       branches:
-         - 'valgrind'
+         - 'valgrind*'
 
     pull_request:
       # Changing this build also gets it to run