feat: token rates resumable polling

[bergeron]

Explanation

Note: This PR accompanies https://github.com/MetaMask/metamask-extension/pull/23507. Read it for more context.

This PR changes the polling strategy for TokenRatesController.

I want to start/stop polling as metamask is opened/closed, to avoid unnecessary requests. But when it's re-opened, I want to "resume" polling rather than "restart".

e.g with a 3 minute polling interval:

• it's been 12 hours since you last opened metamask, so fetch now.

• it's been 1 minute since you last opened metamask, so schedule a fetch in 2 minutes.

I'm storing the last poll time so the interval can be maintained across starts/stops.

Open to alternatives and will write tests if concept ack.

References

Changelog

@metamask/package-a

• <CATEGORY>: Your change here
• <CATEGORY>: Your change here

@metamask/package-b

• <CATEGORY>: Your change here
• <CATEGORY>: Your change here

Checklist

• [ ] I've updated the test suite for new or updated code as appropriate
• [ ] I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• [ ] I've highlighted breaking changes using the "BREAKING" category above as appropriate