Add figure tests as an option

### Describe the feature

This involves changes to:

* [`tox.ini`](https://github.com/sunpy/sunpy/blob/main/tox.ini#L87)
* [Circle CI config](https://github.com/sunpy/sunpy/tree/main/.circleci)
* [test helpers](https://github.com/sunpy/sunpy/blob/main/sunpy/tests/helpers.py#L61-L101)
* Giles config for figure test reports

### Proposed solution

_No response_