.github: workflows: Adopt cargo-nextest and add gstreamer plugins-bad

Switch CI from cargo test to cargo nextest run for parallel test
execution with per-test timeout enforcement.

Changes to .github/workflows/rust.yml:
- Add gstreamer1.0-plugins-bad to apt dependencies (required by
  some integration test pipelines that use elements from plugins-bad)
- Install nextest via taiki-e/install-action@nextest
- Replace `cargo test --verbose --locked` with
  `cargo nextest run --verbose --no-fail-fast --locked`

Add .config/nextest.toml with:
- 120s slow-timeout with terminate-after=2 (kills hung tests)
- A `camera` profile with threads-required=1 override for
  remote_integration:: tests, which share a single MCM instance
  on the remote host and must run sequentially
  (usage: cargo nextest run --profile camera)

Author: joaoantoniocardoso

.config/nextest.toml

@@ -0,0 +1,14 @@
+[store]
+dir = "target/nextest"
+
+[profile.default]
+retries = 0
+slow-timeout = { period = "120s", terminate-after = 2 }
+
+# Camera-mode remote tests share a single MCM instance on the remote host
+# with fixed ports and limited resources. They must run sequentially.
+# Usage: cargo nextest run --profile camera
+[profile.camera]
+[[profile.camera.overrides]]
+filter = "test(/^remote_integration::/) & binary(integration)"
+threads-required = 1

.github/workflows/rust.yml

@@ -86,7 +86,11 @@ jobs:
           gstreamer1.0-x \
           gstreamer1.0-nice \
           gstreamer1.0-libav \
-          gstreamer1.0-plugins-ugly
+          gstreamer1.0-plugins-ugly \
+          gstreamer1.0-plugins-bad
+
+    - name: Install nextest
+      uses: taiki-e/install-action@nextest
 
     - name: Run tests
-      run: cargo test --verbose --locked
+      run: cargo nextest run --verbose --no-fail-fast --locked