Rename partner_logo to affiliate_logo and update core models/tests

[drakeredwind01]

Fixes #replace_this_text_with_the_issue_number

What changes did you make?

Why did you make the changes (we will use this info to test)?

Screenshots of Proposed Changes Of The Website (if any, please do not screen shot code changes)

Visuals before changes are applied

Visuals after changes are applied

[fyliu]

@drakeredwind01 You need to fill in the PR description.

• The issue number at the top links the PR to the issue.
• The changes portion I usually look at the code changes and say what they are
• The reasons should answer the question "what does the project gain from making this change?"
• You can skip the screenshots or attach what it looks like in the admin site, before and after. See this other PR description and do something like that.
• Also, you should havae assigned a reviewer. It sets me as the reviewer after I did a review. Once you're ready, be sure to click the "re-request view" icon next to the reviwer at the top right.