Mention Copilot Pro Trial / Copilot Pro in upgrade hover

[cwebster-99]

Testing #296983

Since we know these users are Copilot Free it may be helpful to callout what they need to upgrade to in the hover. We should say "Try Copilot Pro for 30 days to access this model" or something along those lines so we communicate the free Copilot Pro trial. The text in the model picker itself could just say "Upgrade" as well

[isidorn]

Thanks for your feedback. I like the hover suggestion. How about "Try Copilot Pro for a free 30 day trial to access this model"?

I do not like just "Upgrade" because it is not know what am I upgrading. Keep in mind that sometimes there will be "Update VS Code", so I want to make this distinct.