Changes in ConfigSource Plugins

[omry]

#1170 requires changes to the implementation of all config sources.
This means that existing config source plugins needs to be changed.

The changes includes the removal of is_primary_config and package_override from the signature of load config, which results in as significantly simpler function.

Below is the load_config function from the FileConfigSource as a reference.

    def load_config(self, config_path: str) -> ConfigResult:
        normalized_config_path = self._normalize_file_name(config_path)
        full_path = os.path.realpath(os.path.join(self.path, normalized_config_path))
        if not os.path.exists(full_path):
            raise ConfigLoadError(f"Config not found : {full_path}")

        with open(full_path, encoding="utf-8") as f:
            header_text = f.read(512)
            header = ConfigSource._get_header_dict(header_text)
            f.seek(0)
            cfg = OmegaConf.load(f)
            return ConfigResult(
                config=cfg,
                path=f"{self.scheme()}://{self.path}",
                provider=self.provider,
                header=header,
            )