[v8.x] backport HTTP/2 security release fixups
Backports of #29399 and #29459.
These solve issues introduced in #29122. There was only one minor conflict (static method vs instance method for a C++ class).
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Backports of #29399 and #29459.
These solve issues introduced in #29122. There was only one minor conflict (static method vs instance method for a C++ class).