Make ERR_count_to_mark() available to providers via 'in' dispatch array

Make ERR_count_to_mark() available to providers via 'in' dispatch array

Functions like ERR_set_mark(), ERR_clear_last_mark(), and ERR_pop_to_mark()
are already passed to the a provider via the 'in' dispatch array of the
provider initialization function (although the documentation did not
mention them).

Also pass ERR_count_to_mark() to the provider the same way, and update
the documentation to mention all four functions.

Signed-off-by: Ingo Franzki <ifranzki@linux.ibm.com>
Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/28073)