feat(oft-solana): don't create multisig if no additional minters

[nazreen]

To test:

LZ_ENABLE_SOLANA_OFT_EXAMPLE=1 LAYERZERO_EXAMPLES_REPOSITORY_REF=#nazreen/oft-solana/rm-unnecessary-multisig-creation npx create-lz-oapp@latest

Test results:

When: no additional minters, Mint Authority is OFT Store
Mint: https://solscan.io/account/LbLqBcGtLQ55X13XWM35FS1rG3v1kdH3amXa9MWqxqs?cluster=devnet
Multisig: not created
Successful cross chain transfers:

• Solana to Sepolia -> https://testnet.layerzeroscan.com/tx/2RkNWRxcRtZW2zQzMtk5CYKfnAiDGM56Xcpgman7S6Wf39GiRVLa5nLWt6gLNtdSswu2X3UuBGJL4kMs8m7ivSwp
• Sepolia to Solana -> https://testnet.layerzeroscan.com/tx/0xca6106aaefd9aacfb3a974aece249e9b8e605d1f028516b0fb2d240d72344bab

When: additional minters provided, Mint Authority is Multisig
Mint: https://solscan.io/token/2H1PMNrahdQjZMpXfv7fdaFyuQjnJXHh7yAwxRqe2Zvc?cluster=devnet
Multisig: https://solscan.io/account/6qM5aYWRuLg6PLmgrJE7bbrYuNoBPg6p6ZxDYHU2Mk8q?cluster=devnet
Successful cross chain transfers:

• Solana to Sepolia -> https://testnet.layerzeroscan.com/tx/3efWEZKKKdohC2wUmg4juRdKwQASWd5TrzBvZpuAHwpSby5xw5reN5vJyxU3fym9dWgRc9HX28PmJe88dnn3qX4g
• Sepolia to Solana -> https://testnet.layerzeroscan.com/tx/0x333bb4fa4dfab959e1d13ca94f589a7d323a6a7380c11987ac0f66720eac2d05

[ryandgoulding]

I am not quite sure about this. We had centralized on using MS as mint authority across this OFT reference. Do you know of any issues @ziming-zung

[ryandgoulding]

Per offline discussion:

Yes, the code for signing works for both cases:
1.	When the mint authority is the OFTStore itself.
2.	When the mint authority is a multisig (1 of N) that includes the OFTStore as one of the signers.