feat: TokenAirdrop disable contract airdrops

[vtronkov]

Description:

• Add validation to check if we airdrop to a contract without an admin key
• Bonus refactor: Move the airdrop max value to the config

Related issue(s):

Fixes #14663

Checklist

• [x] Documented (Code comments, README, etc.)
• [x] Tested (unit, integration, etc.)