chore: undelegate/finalize simplification

[crypto-vincent]

Summary

This PR attempts to simplify and de-risk the flow of the undelegate and finalize IXs.

Details

Before this PR, the undelegate IX effectively was a superset of the finalize IX.
Now we expect the finalize IX to be called right before the undelegate (in order for it to succeed)

Additionally this PR simplifies the lamport settling code, while also clarifying the difference between the "undelegation_buffer" used only during the undelegate IX and the regular "buffer" used during the delegate IX.

Greptile Summary

This PR simplifies the delegation program's state management by removing commit-related functionality and consolidating lamports handling logic.

• Removed commit state/record PDAs from undelegate instruction and processing, streamlining the undelegation flow
• Added new undelegation_buffer_seeds_from_delegated_account macro and PDA function in src/pda.rs for clearer buffer management
• Moved settle_lamports_balance function from utils into finalize.rs where it's primarily used
• Removed lamports.rs utility module as part of consolidating lamports handling logic
• Simplified CPI process for external program calls in undelegation

[greptile-apps]

_{6 file(s) reviewed, 3 comment(s)
Edit PR Review Bot Settings | Greptile}

[GabrielePicco]

Left few comments, but LGTM overall! Thanks @crypto-vincent