Add Oracle copyright header format check to jcheck

Updating copyright years in headers is often causing follow on issues due to human error with formatting, typically forgetting the trailing comma. We are currently missing accessible tools for automatically verifying the copyright header format. Adding an elementary check for this to jcheck would help reduce such noise by catching issues earlier.

Note that this feature is only about verifying the format of Oracle copyright headers. It will, for example, not make any attempt at verifying that files have the correct header, or that the copyright years are correct. These are things that need human inspection.