Add toolbar icon for AI Chat

[Bunn]

Task/Issue URL: https://app.asana.com/0/1204167627774280/1208530288219893/f
Tech Design URL:
CC:

Description:
Add toolbar icon for AI Chat

Steps to test this PR:

1. Go to settings
2. Check the AI Chat toolbar icon option
3. Validate the toolbar icon is visible
4. Click the toolbar icon, check that AI Chat is opened
5. Right click in the toolbar icon, check if you can dismiss it
6. Right click in the toolbar, check you have the option to show the toolbar icon from there

[github-actions]

	Warnings
⚠️	PR has more than 500 lines of code changing. Consider splitting into smaller PRs if possible.

	Messages
📖	You seem to be updating localized strings. Make sure that you request translations and include translated strings before you ship your change. See Localization Guidelines for more information.

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