Allow users to upload .edgerc file to specify credentials

Note that the 7.x-3.x branch does not currently allow uploading a .edgerc file, but it does allow specifying the path to the .edgerc file on the server.

As I need this functionality, I'm currently working on an initial patch for this issue.

Here's my initial attempt at the patch. One notable difference between the D7 and D8 version here is that the form I didn't port any of the #element_validate functions.

Mainly, I just wanted to make sure everyone is okay with this approach first.

I went ahead and ran the tests. For clarification, those 4 test failures are already occurring on the main branch, so they aren't the result of this patch.

It's worth noting the unit tests I wrote didn't get ran above. There is a separate issue with unit tests that needs to be resolved first: #2950260: Unit tests aren't running

+1 for #4

Now that #2950260: Unit tests aren't running has been merged, this needs to be rerolled. I'm working on it now.

Rerolled. We should now see the unit test results included in the Drupal CI run.

Ack... That was supposed to go in the comment, not the summary. Let's try that again.

Okay I can confirm that we see testSetupEdgeRc running and passing now. The others are still failing, but that's another issue for another day.

+1 for #10

I've gone ahead and merged this functionality in. In regards to my comment in #4 above, it doesn't appear we have validation for any other fields either, so I've created a separate issue for evaluated form validation on the module as a whole: #2950847: Form validation and marking this issue as fixed.