[FEATURE] @Synchronized should check and warn if j.u.c.l.Lock var

[rzwitserloot]

When using the explicit form of synchronized, e.g. @Synchronized("myVar"), try to detect (it's not a perfect science without resolution, but the vast majority are detectable without resolution) if the field being locked on is of a lock type. If so, warn, because that is exceedingly rarely what you actually wanted, and I can imagine a lombok user thinking that Synchronized("someLockVar") would instead acquire the lock at top of method, not relinquishing it until a finally block at bottom of method.

Example

import java.util.concurrent.locks.*;

public class Example {
    private final Lock lock = new ReentrantLock();

    @Synchronized("lock") public void foo() {}
}

This code should emit a warning: synchronizing on an instance of java.util.concurrent.locks.Lock; that is extremely unlikely to be what you wanted.

See also issue #610