chore(drive-abci): IdentityCreate validation follow-ups from #5431 #5442

Follow-ups from the review of #5431, deferred to keep rc.3 small:

• Move the IdentityCreate identity-id check from advanced structure v1 into a basic-structure version (it reads only the transition), and drop the separate early copy in check_tx.
• Restore a test where, after a charged IdentityCreate failure, the same keys re-signed with a higher user_fee_increase succeed.
• Add a credit-conservation check to the new IdentityCreate block tests (they run through a local process_block that skips block-end fee distribution).
• Remove duplicated test helpers and the redundant asset-lock transaction hashing on the check_tx path.