Some fixes

[a5-pickle]

For #650

TBTC:

• Rename Tbtc -> Config.
• Make Config PDA of TBTC Program instead of using generated keypair (if this were not a PDA, the program can be initialized multiple times).
• Remove payer when authority can pay lamports.
• Leverage Anchor 0.28 features like InitSpace derived trait and access_control macro.
• Remove recipient as required account for recipient token account.
• Fix tests.

Wormhole Gateway (unfinished):.

• Add wormhole-anchor-sdk as dependency.
• Add Custodian account to hold config data and act as mint authority.
• Rename send_tbtc to send_tbtc_to_gateway (for now, need to either add another instruction to send to network without gateway OR make this instruction handle the case where a gateway does not exist).

TODO:

• Add two-step owner transfer to TBTC program.
• Add message encoding/decoding.
• Add Token Bridge CPI to transfer wrapped tokens with message.
• Read Posted VAA account to redeem token bridge transfer with message.
• Audit remaining Gateway logic (commented out receive_tbtc module so program compiles).
• Add Wormhole Gateway tests.

NOTE: This is still a work in progress. What can be done in the meantime is:

• Add Wormhole Gateway tests (just a framework is fine, I can add some more in the morning).
• Think about the optimal design of whether split instructions vs all-in-one instructions make sense (e.g. send_tbtc vs gateway and non-gateway separated).