Treat unknown frames as a protocol error

Treat unknown frames as a protocol error

From RFC9000, section 19.21 "An extension to QUIC that wishes to use a new
type of frame MUST first ensure that a peer is able to understand the
frame". So if we receive an unknown frame type from a peer we should treat
it as a protocol violation. In fact we ignore it, and ignore all the
contents of the rest of the packet and continue on regardless.

Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20030)