Refactor: Replace recursive retry with iterative loop in NewKeyForDirectICAP

[prestoalvarez]

This PR refactors the NewKeyForDirectICAP function to use an iterative approach instead of recursion for key generation retries.

Changes:

• Replaced recursive call return NewKeyForDirectICAP(rand) with an infinite for loop
• Moved key generation logic inside the loop
• Early return when valid key is found (strings.HasPrefix(key.Address.Hex(), "0x00"))