Adds UI to open Data Explorer files as plaintext

[samclark2015]

Adds UI affordance in Data Explorer toolbar to open as text file. The button is available only when *.[csv/tsv] files are open (and disabled when binary files or runtime variables are displayed).

Addresses #5206

e2e: @:data-explorer

Release Notes

New Features

• Adds UI affordance in Data Explorer toolbar to open as text file

Bug Fixes

• N/A

QA Notes

Updated existing Data Explorer e2e tests to ensure button is visible when feature is available, and hidden when not. Also added tests to ensure the correct file is opened in a text editor when action is invoked.

[github-actions]

E2E Tests 🚀
This PR will run tests tagged with: @:critical @:data-explorer

^{readme  valid tags}

[wesm]

I didn't review the code itself, but the feature works well here for a CSV file

There's a bit of a quirk when the the button is disabled -- it still has a hover state that makes it look clickable even though the text is grayed out:

I also noticed that this button is visible for the data explorer even when it isn't the headless/DuckDB variety. How hard to you think it would be to hide this button altogether when it isn't applicable? For example, this button would never be usable by a data explorer originating from an R or Python kernel session

[samclark2015]

Thanks for the feedback!! I just pushed a change so the button is indeed hidden when unavailable.

Re. the hover state quirk: I imagine this is resolved with the above change, but curious how you got the buttons on the left. My default editor config displays them on the right of the action bar:

[wesm]

I think it's just because I had the Action Bar enabled, if you run the Toggle Action Bar command, the action bar buttons move from the right side as small buttons to a dedicated row with the text beside them