chore: Silence/Resolve Clippy lints + reformat + CI work

[duesee]

This makes rustfmt and Clippy happy. I believe that the added allows are apppropriate. But better to be careful :-)

Also, I'm trying to resolve a few CI issues: Here, we need to agree how to resolve the dependency issues (explained below).

Further, cargo test (w/o) --workspace failed but CI was happy. This is, I believe, because --workspace pulls in additional dependencies. Thus, the examples in the doc failed because provider is not a default feature. And in CI, we always test with --workspace. cargo-hack is maybe worth a try.

[duesee]

• Clippy
• Rustfmt
• Rust 1.61.0: package which v4.4.2 cannot be built because it requires rustc 1.63 or newer, while the currently active rustc version is 1.61.0
  • Not sure how to proceed here. Increase MSRV? Downgrade which?
• minimal-versions: error: package regex-automata v0.4.3 cannot be built because it requires rustc 1.65 or newer, while the currently active rustc version is 1.61.0
  • Not sure how to proceed here. Increase MSRV? Downgrade regex-automata?
• test/{beta,nightly]: unused import: MechanismErrorKind
  • Not sure what happens here... investigating.

[duesee]

I'll need your advice here, @dequbed. I'll try to figure out what's up with the unused imports. But I think you need to tell me how to proceed with MSRV.

$ cargo tree
rsasl v2.0.1
(...)
├── libgssapi v0.6.4
(...)
│       [build-dependencies]
│       └── bindgen v0.64.0
(...)
│           ├── regex v1.10.2
│           │   ├── regex-automata v0.4.3
│           │   │   └── regex-syntax v0.8.2
(...)
│           └── which v4.2.2
│               ├── either v1.6.0
│               └── libc v0.2.95
(...)