Implement `preHandle()` and `pureChecks()` methods in `TokenAirdropHandler`

[Yosif Touma]

• preHandle - in the TokenAirdropTransactionBody we have the same TokenTransferList as CryptoTransferHandler. We can see how CryptoTransferHandler.preHandle is implemented and do something similar(or even reuse some of the code)

• pureChecks - similar to CryptoTransferHandler - we can reuse some of the logic there

• For more details about the implementation: #12794