cli: Add commands to create valid SPL Multisig and set mint authority

[nvsriram]

This PR adds:

• Add create_spl_multisig <multisigMemberPubkey...> command that mimics spl-token create-multisig to create valid SPL Multisig.
• Add set-mint-authority <newAuthority> command that sets mint authority based on version:
  • If version < 3.x.x: calls spl.setAuthority directly
  • If version >= 3.x.x: calls acceptTokenAuthority
  • Also handles cases where newAuthority is a valid SPL Multisig via the --multisig flag

[nvsriram]

For local testing, I used a demo Solana devnet deployment: 8y2hh2wGnagy8wc8Fe8xsjUtLSHnzFbiPmFNrext4jHm
I tested the commands first using version 2.0.0 to ensure the correct errors were thrown. Then after upgrading to local 3.0.0 version, tested the commands again.

[tonyjin]

Could you separate the work for the TODO refactor from the new functionality to make this easier to review?

[nvsriram]

Could you separate the work for the TODO refactor from the new functionality to make this easier to review?

The TODO refactor refers to this commit: a385a5b. As it is very small in scope. I added it with this PR. However, if you think it makes it easier if it were moved out, I can undo that commit.

On a similar note, I've split the commits based on features so it might be easier to review the commits one-by-one.

[dvgui]

@nvsriram similar to what @tonyjin asked. I would prefer to have a PR with specific additions for this feature, and we can open a new one for code indentation and maybe some housekeeping, like reorganising functions to more files for better readability and structure.

[nvsriram]

@nvsriram similar to what @tonyjin asked. I would prefer to have a PR with specific additions for this feature, and we can open a new one for code indentation and maybe some housekeeping, like reorganising functions to more files for better readability and structure.

Sounds good, will do that then.
For this PR, I'll revert all commits except 25d413c (create-spl-multisig) and 5cb032e (set-mint-authority).
I'll move the remaining commits to another follow-up PR.

[evgeniko]

lgtm