Implement cache prefetch for account data

[daledupreez]

Related to #4637

Changes proposed in this Pull Request:

This PR builds upon the initial cache prefetch work in #4637 to support prefetching account data. Most of the framework for this was in the previous PR, so this PR is really adding some configuration to set up prefetching for account data 10 seconds before cache expiry, and adding a flag to the code that fetches the account data to bypass the cache.

Testing instructions

TBD

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• Covered with tests (or have a good reason not to test in description ☝️)
• Tested on mobile (or does not apply)

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Post merge

• Added testing instructions to the Release Testing Instructions wiki page (or does not apply)
• Added the needs docs label (or does not apply)
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