ENH: Add support for more placeholders in `guess_datetime_format`
#### Is your feature request related to a problem?

We recently realized that `pandas.core.tools.datetimes.guess_datetime_format` outputs an incorrect format string `"Tue %d %b %Y %H:%M:%S AM"` for the datetime `"Tue 24 Aug 2021 01:30:48 AM"`, which otherwise is parseable by `dateutil.parser.parse`.

#### Describe the solution you'd like

Since `"Tue 24 Aug 2021 01:30:48 AM"` is parseable by `dateutil.parser.parse` and `guess_datetime_format` is based on that function, it seems reasonable that `guess_datetime_format` should produce a correct format string when given this example datetime.

#### API breaking implications

I believe modifying `guess_datetime_format` to support more formats placeholders should be a backwards compatible change.

#### Describe alternatives you've considered

Not sure that there are any.

#### Additional context

```python
from pandas.core.tools.datetimes import guess_datetime_format

# actual
assert guess_datetime_format("Tue 24 Aug 2021 01:30:48 AM") == "Tue %d %b %Y %H:%M:%S AM"

# expected
assert guess_datetime_format("Tue 24 Aug 2021 01:30:48 AM") == "%a %d %b %Y %H:%M:%S %p"
```

I already have a PR up for this here: #43900 