Increase the upper limit on group name length

Increase the upper limit on group name length

While all the standardized groups would fit within the old limit,
with the addition of providers, some might want to experiment with
new and unstandardized groups. As such, their names might not fit
within the old limit.

Define it as GROUP_NAME_BUFFER_LENGTH with value 64.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/14502)