HIP-904: Allow max_automatic_token_association to accept -1

[RickyLB]

Signed-off-by: Ricky Saechao ricky@launchbadge.com Description:

This PR contains HIP-904 related feature that allowing unlimited max automatic token associations to an account.

Related issue(s):

• https://github.com/hashgraph/hedera-sdk-rust/issues/791
• https://github.com/hashgraph/hedera-sdk-rust/issues/790

Fixes #

Notes for reviewer:

Checklist

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