src: run clippy and fix issues

[jaudiger]

Very similar to https://github.com/nushell/nu-ansi-term/pull/58 but on src folder this time

[sholderbach]

Before we consider this, we are currently lacking a MSRV checking CI step. While Nushell itself is pretty bleeding edge we have a bunch of large crates that are more conservative about MSRV as dependents (e.g. tracing-subscriber is on 1.63.0). Out of courtesy it may be best to make sure we can maintain the MSRV until there are clear needs for more recent language features (a contentious one could be constification)

If this is not MSRV bumping I would be fine with landing it after review, but we will probably wait on shipping until a necessary bugfix/new feature arrives.

[jaudiger]

I checked this morning of the two PRs I opened were raising the MSRV with the tool cargo-msrv. From my testing, the MSRV is not affected on both branches:

cargo msrv
Fetching index
Determining the Minimum Supported Rust Version (MSRV) for toolchain aarch64-apple-darwin
Using check command cargo check
Check for toolchain '1.67.1-aarch64-apple-darwin' succeeded

Check for toolchain '1.61.0-aarch64-apple-darwin' failed with:
┌───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ error: package `nu-ansi-term v0.50.0 (/Users/jaudiger/Development/git-repositories/jaudiger/nu-ansi-term)` cannot be built because it requires rustc 1.62.1 or newer, while the currently active rustc version is 1.61.0                                                                                                                          │
└───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
Check for toolchain '1.64.0-aarch64-apple-darwin' succeeded
Check for toolchain '1.62.1-aarch64-apple-darwin' succeeded
   Finished The MSRV is: 1.62.1

Please let me know if there is anything else I could do. If you prefer to split the PR and focus on one work at a time, I'm also okay.

[kubouch]

When I run cargo clippy in the src/ folder, nothing shows up.