Allow overriding of defaults list and hydra node regardless of node schema

[omry]

Given this primary config node:

@dataclass
class Config(DictConfig):
  name: str = MISSING
  age: int = MISSING

cs = ConfigStore.instance()
cs.store(name="config", node=Config)

It does not mention the hydra node or the defaults list.
This means that overriding either from the corresponding config.yaml file will be rejected per the schema.

Those two fields should be whitelisted to allow the following config.yaml to be validated against this schema without issues.

# defaults list
defaults:
  - hydra/job_logging: disabled

# hydra node
hydra:
  job:
    name: test

# and some user config
name: foo
age: 12