[Analytics] Replace _execute_action with Custom Command

[BrodyHughes]

Fixes BX-1625

What changed (plus any additional context for devs)

Currently our extension uses _execute_action for the Alt+Shift+R shortcut to open the popup. While functional, this reserved command doesn't dispatch any events we can hook into for analytics. From documentation:

The _execute_action (Manifest V3), _execute_browser_action (Manifest V2), and _execute_page_action
(Manifest V2) commands are reserved for the action of trigger your action, browser action, or page action 
respectively. These commands don't dispatch [command.onCommand] events like standard commands.

This PR replaces _execute_action with a standard command that checks command.onCommand for the execution of this shortcut, and then runs chrome.action.openPopup() in our background.js service-worker script. This gives us identical popup opening behavior while allowing us to track shortcut usage through the command.onCommand listener.

The change does not affect users at all; the shortcut remains the same and popup opening performance is unchanged since we're using Chrome's native popup API.

What to test

• Does extension opening shortcut work identical to how it did before?
• Does analytics for it populate?

[linear]

BX-1625 Add tracking on usage of Option-Shift-R to open the BX

[walmat]

Any performance implications to always listening to chrome commands? Also, any need for other browser support?

[BrodyHughes]

Any performance implications to always listening to chrome commands? Also, any need for other browser support?

i dont think it should have any performance implications since it's event-driven and only runs when a keyboard shortcut is pressed. I did assume firefox would work with this but i dont think it does. ill check / fix that today.

[DanielSinclair]

Moved to WIP since e2e is failing as a side effect; maybe expecting different key registration