Validate and Update pureChecks() in CryptoGetAccountBalanceHandler

[mhess-swl]

This handler could add the following pure checks:

• balanceSource != UNSET
• if balanceSource == ACCOUNT_ID: accountID is valid
  • shard > -1,
  • realm > -1
  • id > 0
  • if (account.kind() == AccountOneOfType.ALIAS) then alias is valid (not null and parseable)
• if balanceSource == CONTRACT_ID: contractID is valid