Refactor visualize tests

[btjanaka]

Description

This PR splits the tests for ribs.visualize into multiple files. Test methods and baseline images are also renamed since their filepaths now include the name of their respective visualization function.

TODO

• [x] Split up tests
• [x] Check that number of tests matches (93)

Questions

Status

• [x] I have read the guidelines in CONTRIBUTING.md
• [x] I have formatted my code using yapf
• [x] I have tested my code by running pytest
• [x] I have linted my code with pylint
• [x] I have added a one-line description of my change to the changelog in HISTORY.md
• [x] This PR is ready to go