fix: avoid overly eager balance lookup

[byte-bandit]

Related Github tickets

• [BUG] Error validating balances too early VolumeFi/paloma#988

Background

We see a lot of error logs when trying to verify validators balances on chains. This is because the established architecture allows to query at arbitrary times, even though Paloma always only uses the current time. The algorithm used to identify the closest block to the given time can lead to resulting in the latest block number, which might not be finalised yet.

For now, we just fall back to the latest block number - 1 in this case, which should work. In the future, we might want to strip out the entire block height search and always use the current block height, as it's using binary search to approximate the block and makes a decent amount of API calls while doing so.

Testing completed

• test coverage exists or has been added/updated
• tested in a private testnet

Breaking changes

• I have checked my code for breaking changes

[taariq]

LGTM!