Have the protoc CLI properly report any parser warnings.

Remove the naming warnings that would be considered noisy if they were suddenly enabled with no easy way to disable the warnings. The upcoming Edition 2024 naming style enforcement feature and a planned corresponding change to the linter which respects NOLINT comments will cover the cases that these warnings would.

The parser appears to have been accidentally silently suppressed on the CLI path all along; while they were reachable on other usages of the parser, those cases are secondary compared to what we consider the main entry point and so no longer having the naming warnings on those should not locally be a major loss.

PiperOrigin-RevId: 716223703