8068995: Cleanup method reference lookup code Summary: Simplify method reference code lookup and generate better/more uniform diagnostics Reviewed-by: vromero

8066843: Messager.printMessage cannot print multiple errors for same source position Summary: Using a DiagnosticFlag to mark diagnostics that should be always printed even if multiple of them have the same source position. Reviewed-by: darcy, jjg, mcimadamore