[v10.x] process: generate list of allowed env flags programmatically
Backport of #22638 with a teeny tiny adjustment (the fixup commits adds a 2 to a regex in the test file to accomodate --expose-http2) – otherwise clean cherry-picks
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Backport of #22638 with a teeny tiny adjustment (the fixup commits adds a 2 to a regex in the test file to accomodate --expose-http2) – otherwise clean cherry-picks