**Apache Airflow version**: 2.1.0

**What happened**:
Airflow logging assume dict_key is type `str`
```
    logging.info("Dictionary where key is int type: %s", modified_table_mapping)
  File "/usr/lib64/python3.6/logging/__init__.py", line 1902, in info
    root.info(msg, *args, **kwargs)
  File "/usr/lib64/python3.6/logging/__init__.py", line 1308, in info
    self._log(INFO, msg, args, **kwargs)
  File "/usr/lib64/python3.6/logging/__init__.py", line 1444, in _log
    self.handle(record)
  File "/usr/lib64/python3.6/logging/__init__.py", line 1453, in handle
    if (not self.disabled) and self.filter(record):
  File "/usr/lib64/python3.6/logging/__init__.py", line 720, in filter
    result = f.filter(record)
  File "/bb/bin/airflow_env/lib/python3.6/site-packages/airflow/utils/log/secrets_masker.py", line 157, in filter
    record.__dict__[k] = self.redact(v)
  File "/bb/bin/airflow_env/lib/python3.6/site-packages/airflow/utils/log/secrets_masker.py", line 193, in redact
    return {dict_key: self.redact(subval, dict_key) for dict_key, subval in item.items()}
  File "/bb/bin/airflow_env/lib/python3.6/site-packages/airflow/utils/log/secrets_masker.py", line 193, in <dictcomp>
    return {dict_key: self.redact(subval, dict_key) for dict_key, subval in item.items()}
  File "/bb/bin/airflow_env/lib/python3.6/site-packages/airflow/utils/log/secrets_masker.py", line 189, in redact
    if name and should_hide_value_for_key(name):
  File "/bb/bin/airflow_env/lib/python3.6/site-packages/airflow/utils/log/secrets_masker.py", line 74, in should_hide_value_for_key
    name = name.strip().lower()
AttributeError: 'int' object has no attribute 'strip'
```

**How to reproduce it**:
Define a dictionary where the type of keys is `int` and print it in any Airflow tasks.

airflow/utils/log/secrets_masker.py
"""Redact secrets from logs"""
    replacer: Optional["RePatternType"] = None
    patterns: Set[str]
    ALREADY_FILTERED_FLAG = "__SecretsMasker_filtered"
    MAX_RECURSION_DEPTH = 5
    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: