Implement a human readable state function for the record layer

Implement a human readable state function for the record layer

This allows querying of the record layer to get a human readable state
string out. This resolves two outstanding TODO comments and enables us
to remove the rstate variable from s->rlayer.

Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18132)