**Description** 

Since sensitive informations in the connection object (specifically the extras field) are now being masked based on sensitive key names, we should consider adding some common sensitive key names.

`private_key` from [ssh connection](https://airflow.apache.org/docs/apache-airflow-providers-ssh/stable/connections/ssh.html) is an examples.

**Use case / motivation**

Extras field used to be blocked out entirely before the sensitive value masking feature (#15599).

[Before in 2.0.2](https://github.com/apache/airflow/blob/2.0.2/airflow/hooks/base.py#L78
) and [after in 2.1.0](https://github.com/apache/airflow/blob/2.1.0/airflow/hooks/base.py#L78
).

Extras field containing sensitive information now shown unless the key contains sensitive names.

**Are you willing to submit a PR?** 

@ashb has expressed interest in adding this.

airflow/utils/log/secrets_masker.py
"""Redact secrets from logs"""
    replacer: Optional["RePatternType"] = None
    patterns: Set[str]
    ALREADY_FILTERED_FLAG = "__SecretsMasker_filtered"
    def __init__(self):
        super().__init__()
        self.patterns = set()
    @cached_property
    def _record_attrs_to_ignore(self) -> Iterable[str]:
        
        
        #
        
        
        record = logging.getLogRecordFactory()(
            
            "x",
            logging.INFO,
            __file__,
            1,
            "",
            tuple(),
            exc_info=None,
            func="funcname",
        )
        return frozenset(record.__dict__).difference({'msg', 'args'})
    def filter(self, record) -> bool: