ci: Setup valid Cargo.lock for depcheck to unblock CI (#22933)

## Which issue does this PR close?

- Closes #22932

## Rationale for this change

`depcheck` stopped working because an underlying dependency released a
non-semver compatible change (`time 0.3.48`, not going to link to the
issue there because people are already spamming it). Because there was
no lockfile, every run pulled the most recent versions for all
dependencies, which don't currently compile.

## What changes are included in this PR?

1. Add lockfile to `depcheck`
2. Make sure to run `depcheck` with `--lock` in CI

## Are these changes tested?

Tested locally

## Are there any user-facing changes?

None

Co-authored-by: Jeffrey Vo <jeffrey.vo.australia@gmail.com>

Author: AdamGS

.github/workflows/dependencies.yml

@@ -50,9 +50,9 @@ jobs:
         with:
           rust-version: stable
       - name: Check dependencies
+        working-directory: dev/depcheck
         run: |
-          cd dev/depcheck
-          cargo run
+          cargo run --locked
 
   detect-unused-dependencies:
     name: Detect Unused Dependencies