ASN.1: extend the possibilities to embed data instead of pointers

Also, when "allocating" or "deallocating" an embedded item, never call
prim_new() or prim_free().  Call prim_clear() instead.

Fixes #3191

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3199)