feat: return tx block height info

[mFragaBA]

addresses #380.

Includes the block where a transaction was included and the account it was executed against in the state sync response. In this PR, we include that information within the existing AccountSummary. A few issues arise from this though:

• first, I couldn't just modify the AccountSummary protobuf message as it's reused in other places. Hence I made a wrapper named AccountUpdate (similar to the NullifierUpdate name).
  • AccountUpdate contains an AccountSummary and a list of TransactionInfo (which in turn contains the transaction ID and block number)
• I had to change a bit select_transactions_by_accounts_and_block_range. Now it returns a mapping account_id => TransactionInfo
• Then, on the sync state handler we need to "merge" the TransactionInfos with the fetched account summaries. This poses a new issue as some transactions might not have a matching account summary if a client with old state does a sync request (@bobbinth mentioned situation where this happens in the issue).
  • By just wrapping the AccountSummary struct, one problem is that the account_id for AccountUpdate is within the optional AccountSummary. So that will require to either modify AccountSummary, to define a new message that stores almost the same info as AccountSummary or to embed the fields within AccountUpdate

Note: This is a POC implementation, made so we can compare this vs. a decoupled approach.

TODO:

• code cleanup
• update documentation

[bobbinth]

Note: This is a POC implementation, made so we can compare this vs. a decoupled approach.

Could you create a PR for the "decoupled approach" as well? Would make it a bit easier to compare the two.

[mFragaBA]

Note: This is a POC implementation, made so we can compare this vs. a decoupled approach.

Could you create a PR for the "decoupled approach" as well? Would make it a bit easier to compare the two.

#386 done!

[mFragaBA]

closing this PR since we ended up going with the decoupled approach on #386