Optimize `CryptoTransferValidator.validateTokenTransfers()` for single crypto transfer

From @OlegMazurov:

> In most cases (single transfer), all those HashSets are created and populated for nothing. A fast path should be possible while the slow path (current implementation) would cover the generic case.

## Background
While doing its validations, `CryptoTransferValidator.validateTokenTransfers()` function maintains a few `HashSet`s for its calculations. The code is correct, but not optimized for the majority case–transfer of a single token.

This ticket is to optimize by removing the unneeded `HashSet`s for the majority case.

## Dependencies
Work with @OlegMazurov to verify performance benefit

Start at CryptoTransferValidator.validateTokenTransfers() and inspect how the HashSets are created and populated for single versus generic token transfers. Work with @OlegMazurov to establish the performance baseline and verify the optimized path preserves validation behavior and improves the single-transfer case.

Written by the indexing model from the issue text.