Fix BIO_get_new_index() to return an error when it is exhausted.

Fix BIO_get_new_index() to return an error when it is exhausted.

Fixes #23655

BIO_get_new_index() returns a range of 129..255.

It is set to BIO_TYPE_START (128) initially and is incremented on each
call.
>= 256 is reserved for the class type flags (BIO_TYPE_DESCRIPTOR) so it
should error if it reaches the upper bound.

Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/23732)