Replace --all with --workspace on cargo test.

According to the official cargo documentation at
https://doc.rust-lang.org/cargo/commands/cargo-build.html `--all` is
deprecated.

"""
--all
Deprecated alias for --workspace.
"""

changelogs/unreleased/ci-rust-cargo-test-workspace-option.yml

+---
+title: "Rust CI template: Replace --all with --workspace on cargo test."
+merge_request: 33517
+author: Markus Becker
+type: fixed

lib/gitlab/ci/templates/Rust.gitlab-ci.yml

@@ -20,4 +20,4 @@ image: "rust:latest"
 test:cargo:
   script:
     - rustc --version && cargo --version  # Print version info for debugging
-    - cargo test --all --verbose
+    - cargo test --workspace --verbose