Add comprehensive linting

[jnbooth]

Enables most Clippy lints.

Most of these changes were automatically applied using cargo clippy --fix. Nearly all of them are simple syntactic adjustments like adding a semicolon at the end of a line. The remaining changes are things like removing unused &self parameters and accepting &str instead of String if ownership isn't necessary.

I can break those up into multiple PRs if that's preferred, but I figured I'd start by putting them all in one place so people can take a look and decide what they think.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (48acbdb) to head (c7a3670).

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #1327   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           75        75           
  Lines        12764     12757    -7     
=========================================
- Hits         12764     12757    -7     

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[ahayzen-kdab]

before we were testing in CI with our MSRV, do we not want to do this now?

Or instead should something like clippy be in it's own runner using a newer Rust toolchain 🤔

[LeonMatthesKDAB]

IMO, clippy could also just be separate runner, as I think it doesn't share many build artifacts with the main build anyhow.

[ahayzen-kdab]

i guess my question would be why are these lints not enabled by default? Do we want to enable so many? I usually follow the defaults for lints as there is sometimes a reason why they are not enabled yet. As otherwise this can become an explosion of debates.

[jnbooth]

No clippy lints are enabled by default as far as I'm aware. The nice thing about making lints opt-out instead of opt-in is that there are a lot of lints and I think most of them are useful—I learned some new best practices in the course of making this PR, such as clippy::ptr_as_ptr. This PR has actually been something I've been working on for a while because it has been a useful exercise for me, and it has yielded other PRs in the process such as #1324 and #1321. So the effort was worthwhile in itself, even if this PR doesn't get merged.