[ENH] Restore download functionality for refactor/new meta getter

[jarmoza]

Closes #427
Closes #416
Fixes #172

Changes proposed in this pull request:

• Refactor of download page to use new meta getter getJsonOutput
• Adds new field and getter for dataDictionary.filename to (re)use for the new output json file
• Download page 'e2e' test checks if a file has has downloaded after button click (solution suggestion found here: https://stackoverflow.com/questions/73971115/how-do-i-list-the-contents-of-the-download-directory-in-cypress-i-need-to-make)
• Adds app state loading code for download page
• Update unit test for meta getter getJsonOutput with mocks for its getters. This overcomes an issue where calling a getter from a getter worked one way in e2e/manual testing but not in unit testing and vice versa.

[surchs]

Very exciting milestone @jarmoza 🎉. We definitely need to celebrate this big achievement with everyone, especially @rmanaem!

The PR looks good, my comments are mostly 🍒 or thoughts. Take a look and decide, then good to squash merge 🧑‍🍳

Once you do, please directly open the next PR to merge dev_... into master! We can deal with any required rebasing in that other PR then.

[surchs]

nice!
One thing I'm noticing here is that because all of the getters have to be stubbed, I'm not sure what we'll do once we encounter some weird edge cases that we'll also want to test. If every one of these needs it's own setup and each setup will be as long as this one, tests may get a bit hard to read.

But for now this reads well!

[jarmoza]

This may be beyond an aesthetic issue actually. Something I've noticed is that debugging the getters if they are plugged in via the import from index.js is not available via console-style debugging. And in fact, it seems that beforeEach is working in a different or at least at a different time to properly setup the variables for each test. I've noticed there's a difference between assigning getters to store.state.getters in beforeEach vs. inside of a test. This is something that should be documented in our Cypress wiki as well.