refactor: remove obsolete persistStoreData flag from PersistentStore, take 2

[codeofdusk]

Details

When we originally introduced PersistentStore during the MV2->MV3 transition, it included a persistStoreData constructor flag which allowed us to gradually transition different stores to using persistence depending on whether we were working with an MV2 or MV3 build. This functionality is now obsolete - all PersistentStore-based stores always use this with a constant true input. This PR removes the obsolete flag.

Motivation

Clean up obsolete code

Context

This is a takeover of abandoned #6300, which was closed due to the flag's usage in Unified. Now that Unified is gone, this change is unblocked.

This diff is quite large – many files are modified, but each modification is relatively small. Happy to split in any way desired to ease review.

Noticed while working on #6233

Pull request checklist

• [n/a] Addresses an existing issue: #0000
• Ran yarn fastpass
• Added/updated relevant unit test(s) (and ran yarn test)
• [n/a] Verified code coverage for the changes made. Check coverage report at: <rootDir>/test-results/unit/coverage
• PR title AND final merge commit title both start with a semantic tag (fix:, chore:, feat(feature-name):, refactor:). See CONTRIBUTING.md.
• [n/a] (UI changes only) Added screenshots/GIFs to description above
• [n/a] (UI changes only) Verified usability with NVDA/JAWS

[DaveTryon]

Seems reasonable. There are a few places where we pass in null for persistStoreData, which would have the same result as passing in false, but these are all in test code and won't impact the actual product