Make the provider context available to encoders

Make the provider context available to encoders

At the moment the provider context is only available to
encoders that encrypt, but it is useful more generally.

A similar change has already been merged to "master" on the
decoder side, this is the mirror change for encoders.  The
only significant difference is that PEM_ASN1_write_bio needed
to be "extended" (cloned) to allow it to pass the provider context
down to the `k2d` function it uses to encode the data.

I had to "hold my nose" and live with the random "20" added to the data
size in order to accomodate encryption with padding, which may produce
one more cipher block than the input length.  This really should ask
the EVP layer about the block length of the cipher, and allocate the
right amount.  This should be a separate fix for both the old
PEM_ASN1_write_bio() and the new PEM_ASN1_write_bio_ctx().

Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/26475)