PROV: Re-implement all the keypair encoders

PROV: Re-implement all the keypair encoders

The base functionality to implement the keypair encoders doesn't
change much, but this results in a more massive amount of
OSSL_DISPATCH and OSSL_ALGORITHM arrays, to support a fine grained
selection of implementation based on what parts of the keypair
structure (combinations of key parameters, public key and private key)
should be output, the output type ("TEXT", "DER" or "PEM") and the
outermost output structure ("pkcs8", "SubjectPublicKeyInfo", key
type specific structures, ...).

We add support for the generic structure name "type-specific", to
allow selecting that without knowing the exact name of that structure.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/13167)