Move the record padding callback fully into the record layer

Move the record padding callback fully into the record layer

We wrap the callback and pass it to the record layer via the dispatch
array, in order to avoid accessing it directly via SSL_CONNECTION.

Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/19198)