feat: add on demand fetching and stale attr to rpc

[zachdaniel]

Resolves #1891

Motivation

We want to trigger a balance fetch on any stale balances when they are retrieved via the API, not only when they are viewed in the UI. So that consumers would know, I added an attribute to the response called "stale" that is set to true when we have determined that the balance is old and is worth checking again. This doesn't mean that the balance is wrong (it will usually be right), it just means that we haven't seen an update for it in the last 24 hours, so we're going to check it again.

Changelog

Enhancements

• Fetch coin balance on demand for API requests.

  • I added an entry to CHANGELOG.md with this PR
  • If I added new functionality, I added tests covering it.
  • If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.
  • I checked whether I should update the docs and did so if necessary

[coveralls]

Pull Request Test Coverage Report for Build 44b9cfc1-d85a-45e9-9958-37c6e1262608

• 12 of 12 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.09%) to 81.893%

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Totals
Change from base Build 782d44e1-3ce0-4d82-befd-9964118470b6:	0.09%
Covered Lines:	4654
Relevant Lines:	5683

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💛 - Coveralls