Batch up NFT balance updates

[JamesSmartCell]

This improves the update speed for NFT balance checks where users have a lot of NFTs (sometimes over 1000) on the same contract. Now there's usually one 1 call to update balances.

Note: next will be to apply this method to TokensService to hugely speed up token balance checking and syncing.

[github-actions]

Pull reviewers stats

Stats of the last 30 days for alpha-wallet-android:

	User	Total reviews	Time to review	Total comments
	seabornlee 🥇	15 ▀▀▀▀	3h 28m ▀	12 ▀▀▀▀▀▀
	JamesSmartCell 🥈	13 ▀▀▀▀	14h 17m ▀▀▀▀	7 ▀▀▀▀
	justindg 🥉	8 ▀▀	20h 33m ▀▀▀▀▀	1 ▀

[codecov]

Codecov Report

Base: 7.60% // Head: 7.59% // Decreases project coverage by -0.01% ⚠️

Coverage data is based on head (d2e23f1) compared to base (f26a468).
Patch coverage: 0.81% of modified lines in pull request are covered.

Additional details and impacted files

@@             Coverage Diff             @@
##             master   #2975      +/-   ##
===========================================
- Coverage      7.60%   7.59%   -0.02%     
  Complexity      857     857              
===========================================
  Files           636     636              
  Lines         42772   42866      +94     
  Branches       4282    4307      +25     
===========================================
+ Hits           3253    3254       +1     
- Misses        39243   39336      +93     
  Partials        276     276              

Impacted Files	Coverage Δ
...ain/java/com/alphawallet/app/entity/EventSync.java	0.00% <0.00%> (ø)
...com/alphawallet/app/entity/tokens/ERC721Token.java	0.00% <0.00%> (ø)
...lphawallet/app/repository/EthereumNetworkBase.java	50.92% <5.88%> (-1.64%)	⬇️
...phawallet/app/ui/WalletConnectSessionActivity.java	0.00% <0.00%> (ø)

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