punycode: update to use WPACKET instead of using custom range checking

punycode: update to use WPACKET instead of using custom range checking

Add test for `.' overflows, remove the output size argument from
ossl_a2ulabel() since it was never used and greatly complicated the code.
Convert ossl_a2ulabel() to use WPACKET for building the output string.
Update the documentation to match the new definition of ossl_a2ulabel().

x509: let punycode handle the '\0' string termination.  Saves a memset(3)
and some size fiddling.  Also update to deal with the modified parameters.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/19591)