Evergreen-py

- Add ChangeLog data

- Add `repeat_patch` function to `EvergreenApi`. This function repeats the tasks and variants of a previous patch.

- `EvergreenApi` constructor now accepts an optional `urllib3.util.Retry` object that can be used to customize http request retry approach.
- RetringEvergreenApi retry logic has been rewritten using `urllib3.util.Retry` instead of `Tenacity` library.
- RetringEvergreenApi re-use same session across different requests.

- Add support for select tests endpoint

- Fix `file_diffs` getter.

- Switch to GitHub merge queue (no code changes)