Fix warnings encountered during unit tests

Currently when running the full test suite over **17,000** warnings are generated:

```
2417 passed, 23 skipped, 87 xfailed, 17879 warnings
```

Some of these warning may be expected, but some should be addressed. This may require mutiple PRs, but we should investigate these warnings and implement fixes where possible. Of immediate concern are the deprecation warnings that might cause tests to break when new versions of dependencies are released:

```
featuretools/tests/primitive_tests/test_num_consecutive.py::TestNumConsecutiveLessMean::test_inf
/dev/featuretools/featuretools/tests/primitive_tests/test_num_consecutive.py:259: FutureWarning: The series.append method is deprecated and will be removed from pandas in a future version. Use pandas.concat instead.
x = x.append(pd.Series([np.inf]))
```

This Dask warning also appears to be quite common and perhaps of concern.
```
featuretools/tests/primitive_tests/test_transform_features.py::test_comparisons_with_ordinal_invalid_inputs[dask_es]
/dev/featuretools/env/lib/python3.9/site-packages/dask/dataframe/core.py:4134: UserWarning:
You did not provide metadata, so Dask is running your function on a small dataset to guess output types. It is possible that Dask will guess incorrectly.
To provide an explicit output types or to silence this message, please provide the `meta=` keyword, as described in the map or apply function that you are using.
Before: .apply(func)
After: .apply(func, meta=('priority_level <= ordinal_invalid', 'object'))

warnings.warn(meta_warning(meta))
```