YANG gen. binding classes should offer a matches(CharSequence input) [or expose Pattern[] patterns public instead private]

In https://git.opendaylight.org/gerrit/#/c/53118/ for NETVIRT-514 I found myself wanting to access the java.util.regex.Pattern in a YANG gen. binding class, but could not because it is private.

It's easy enough to recreate it from the public List<String> PATTERN_CONSTANTS, but perhaps you would consider exposing it as a public static final Pattern[] PATTERNS; as well?

Not sure if this has to be depending on MDSAL-237 Binding Specification Java v2, or could already be done in v1 - what's the risk, after all?

I'll also file a separate bug proposing to offer an additional utility method, this issue is to focus particularly just on exposing the Pattern publicly.