Introduce workspace dependencies (#12043)

# Description
This PR introduces [workspaces
dependencies](https://doc.rust-lang.org/cargo/reference/workspaces.html#the-dependencies-table).
The advantages are:
- a single place where dependency versions are declared
- reduces the number of files to change when upgrading a dependency
- reduces the risk of accidentally depending on 2 different versions of
the same dependency

I've only done a few so far. If this PR is accepted, I might continue
and progressively do the rest.

# User-Facing Changes
N/A

# Tests + Formatting
- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`

# After Submitting
N/A

crates/nu-test-support/Cargo.toml

@@ -17,6 +17,6 @@ nu-glob = { path = "../nu-glob", version = "0.91.1" }
 nu-utils = { path = "../nu-utils", version = "0.91.1" }
 
 num-format = "0.4"
-which = "6.0.0"
-tempfile = "3.10"
+which = { workspace = true }
+tempfile = { workspace = true }
 hamcrest2 = "0.3"