ENCODER & DECODER: Make a tighter coupling between en/decoders and keymgmt

ENCODER & DECODER: Make a tighter coupling between en/decoders and keymgmt

If there are keymgmts and en/decoders from the same provider, try to
combine them first.

This avoids unnecessary export/import dances, and also tries to avoid
issues where the keymgmt doesn't fully support exporting and importing,
which we can assume will be the case for HSM protected keys.

Fixes #15932

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15933)