CI: install GLib/GStreamer dev packages for Rust build job

[Copilot]

The build GitHub Actions job failed because the Rust dependency chain (glib-sys via default GStreamer backend) requires system GLib metadata (glib-2.0.pc), which was not available on the runner. This PR updates the workflow to provision required Linux packages before cargo build/cargo test.

• Root cause

  • glib-sys custom build script invokes pkg-config for glib-2.0 and exits when glib-2.0.pc is missing.

• Workflow change

  • Added a dependency install step in .github/workflows/rust.yml before build/test.
  • Installs:
    • pkg-config
    • libglib2.0-dev
    • libgstreamer1.0-dev

• Patch shape (minimal)

  - name: Install system dependencies
    run: sudo apt-get update && sudo apt-get install -y \
      pkg-config libglib2.0-dev libgstreamer1.0-dev

[kulpae]

looks good!