Setup global cargo lint configuration (#13691)

# Description
`cargo` somewhat recently gained the capability to store `lints`
settings for the crate and workspace, that can override the defaults
from `rustc` and `clippy` lints. This means we can enforce some lints
without having to actively pass them to clippy via `cargo clippy -- -W
...`. So users just forking the repo have an easier time to follow
similar requirements like our CI.

## Limitation

An exception that remains is that those lints apply to both the primary
code base and the tests. Thus we can't include e.g. `unwrap_used`
without generating noise in the tests. Here the setup in the CI remains
the most helpful.

## Included lints

- Add `clippy::unchecked_duration_subtraction` (added by #12549)
# User-Facing Changes
Running `cargo clippy --workspace` should be closer to the CI. This has
benefits for editor configured runs of clippy and saves you from having
to use `toolkit` to be close to CI in more cases.

crates/nu-cmd-plugin/Cargo.toml

@@ -9,6 +9,9 @@ version = "0.97.2"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
+[lints]
+workspace = true
+
 [dependencies]
 nu-engine = { path = "../nu-engine", version = "0.97.2" }
 nu-path = { path = "../nu-path", version = "0.97.2" }
@@ -17,4 +20,4 @@ nu-plugin-engine = { path = "../nu-plugin-engine", version = "0.97.2" }
 
 itertools = { workspace = true }
 
-[dev-dependencies]
+[dev-dependencies]