CompactBlockProcessor fetches UTXOs in a weird order

[str4d]

Currently refreshUtxos is triggered every time we finish scanning an individual block range:

zcash-android-wallet-sdk/sdk-lib/src/main/java/cash/z/ecc/android/sdk/block/processor/CompactBlockProcessor.kt

Lines 478 to 489 in 90bff31

	when (batchSyncProgress.resultState) {
	SyncingResult.UpdateBirthday -> {
	updateBirthdayHeight()
	}
	SyncingResult.EnhanceSuccess -> {
	Twig.info { "Triggering transaction refresh now" }
	// Invalidate transaction data
	checkTransactions(transactionStorage = repository)
	batchSyncProgress.range?.start?.let {
	refreshUtxos(account = Account.DEFAULT, startHeight = it)
	}
	}

Note that we refresh UTXOs from the start height of the block range that was scanned. Given that we do non-linear scanning now, this means we're potentially fetching weird subsets of the UTXO set for the wallet.

When I added transparent UTXO fetching to zec-sqlite-cli in https://github.com/Electric-Coin-Company/zec-sqlite-cli/pull/23, I instead implemented it by, just after calling update_chain_tip and before any shielded scanning in a scan cycle, fetching all UTXOs starting at the block-fully-scanned height (which is always increasing, and means we fetch the full block range where we have not scanned all shielded information).

We should do something similar here, adjusted for appropriate re-fetch frequency depending on how the sync state machine is implemented here.