solana: Add function comments; document some anchor constraints

[johnsaigle]

• Add linting directives for cargo dylint to ignore ownership and singer checks in particular cases
• Add function documentation and some clarifying notes

See also: #232. This PR contains commits from #232.

[johnsaigle]

@kcsongor I would love your input here regarding the accuracy of my comments and the security concerns about the ownership checks

[kcsongor]

great!

[johnsaigle]

@kcsongor Could you re-review when you get some time? This resolves all of the false positives.

If it looks good to you and we merge it, we can also close #232 as this PR contains all of those commits

[kcsongor]

I like the comments, but lints themselves seem redundant. Looks like it flags false positives for things that anchor checks. How about we drop the linter and just keep the comments? The convention is moving those account security related comments above the account like

/// CHECK: <comment here>
pub account_foo: Account<...>

[johnsaigle]

@kcsongor Did you change your mind from what we talked about in other PR? #232 (comment) 😅

Ultimately, I think you're right. After working with them a bunch I think these lints are meant for Solana itself more than Anchor. I can rework this PR so that contains only the function comments and the security notes formatted as CHECK: statements

[kcsongor]

Apologies for flip-flopping on this! As you worked out all the false positives I think the picture it paints is that it's not as useful as it first seemed.

[johnsaigle]

@kcsongor I'm actually unsure about this annotation. Do we want to constrain the Transceiver in some way?
This is a privileged action so it's probably OK.

[johnsaigle]

I duplicated a lot of this effort in #330 but some of the comments in this PR are still useful. #330 should probably be merged first and I can rebase this PR on that one