Allow users to set a limit on how many tokens an app can use

Similar to a "gas limit" in metamask.

The way I'm thinking we could implement it, but open to other ideas:

We add a field to Origin that indicates the limit (in $), and another field with how much has been used.
We deprecate the permission field. Instead, "allow" translates to limit === -1 (e.g. infinite), and "ask" translates to limit === 0 (ask every time)
We change the PermissionRequest.tsx ui to allow users to customize the limit per app, using a slider. limit defaults to 0.
Every completion request then updates used
Some module is responsible for accounting (would be nice to track overall $ used in a separate manager)
requestPermission skips over "limited" origins for requests that have a maxTokens param and are under the limit with that param included in accounting
Once we hit the limit, requestPermission will fire up the modal again, defaulting to the same limit as last time but allowing the user to change the app's permissions again if they want to. used is reset to zero when the user clicks allow, and at the end of the transaction, it's updated again.

alexanderatallah / window.ai