sdk: append the payer Permission account on feed and user commands

[martinsander00]

Summary of Changes

• The Rust SDK appends the payer Permission account on doublezero feed create, feed delete, feed update, user delete, and user update when that account exists and the serviceability program owns it.
• A signer that only holds feed-authority or user-admin on that account was denied with program error 0x8 (NotAllowed) because those commands never sent the extra account.
• doublezero user create is unchanged. That instruction counts accounts to detect an optional tenant.

Part of https://github.com/malbeclabs/infra/issues/2343

Testing Verification

• Feed create has a missing-account case and a present-account case. The present case expects the Permission account last on the instruction.
• Feed delete, feed update, user delete, and user update stub a missing Permission account so the instruction matches the builder with no extra account.