DECODER: Use the data structure from the last decoder to select the next

DECODER: Use the data structure from the last decoder to select the next

Any decoder can now also declare the name of the data structure for
the object it decoded in the OSSL_PARAM array they pass back to the
decoding process.  The decoding process will use that as another
criterion to select the next decoder in the chain to consider.

Together with declaring the data type, this becomes a means to refine
how the decoded data is treated along the chain.

Fixes #13539

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/14233)