Extend `mask` of `ssl_method_st` to 64-bit

Fixes #23260: The bit count for `SSL_OP_*` flags has exceeded 32 bits, making it impossible to handle newer flags and protocol extensions with the existing 32-bit variables. This commit extends the `mask` field in the `ssl_method_st` structure to 64-bit, aligning them with the previously extended 64-bit `options` field.

Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Paul Dale <ppzgs1@gmail.com>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/24692)