Squads Integration

[sohrab-]

Rather than "Send", submit the "draft" Transaction to a Squads multisig.

• Add a drop-down switch to Send button
• Provide fields for multisig and authority index in transaction header
• Support devnet and mainnet
• Later on, provide template instructions for program upgrade, stake, stake pool, vote, etc.

[sohrab-]

Alternatively, just convert to a Sqauds transaction and load that into the client to run

[sohrab-]

The main implementation is done in https://github.com/labeleven-dev/bettercallsol/commit/7c9756f7e0c5a69100d625efb3f2f02fa3cdda88.

"Template instructions" are not required as current Anchor features will cover that.