Android: Fixes #10152: Fix broken plugin API: editor.execCommand

[personalizedrefrigerator]

Summary

Fixes and adds tests for the Joplin 'editor.execCommand' command. This fixes two issues related to the command:

1. The editor command being executed with editor.execCommand was incorrectly extracted from the arguments list.
2. The value of this was incorrect for legacy CM5 commands executed with editor.execCommand.

Fixes #10153.

Notes

This does not completely fix the "scroll to heading" logic in the outline plugin -- it uses a legacy CM5 API to scroll to the line containing a header that isn't supported on mobile (because of how we handle scroll to work around this bug). It does, however, allow similar commands to run.

Testing

1. Install the outline plugin
2. Open a note with headings
3. Open the outline plugin's panel
4. Click on a heading
5. Verify that no error is logged (even if the heading isn't scrolled to)
6. Add a breakpoint and verify that the command is run
   • This can be done by opening the note editor with Chrome's dev tools (chrome://inspect).

This has been tested successfully on Android 12.