feat(exporter): implement subprocess execution with active stall watchdog and TCP metrics (#26)

- Replace in-process iperf3 C binding with subprocess execution
- Add active I/O stall detection and connect-timeout
- Expose TCP retransmissions, mean RTT (ms), and exporter cycle timestamp
- Upgrade Dockerfile to Python 3.12 running as non-root user (nobody)
- Fix testTimeout/testDuration environment variable mapping in Helm chart
- Remove dead TrueCharts prometheus-operator chart dependency
- Add unit tests for exporter metric parsing and stall handling
- Switch tooling from devbox to mise

Co-authored-by: Malarbase <malarbase@gmail.com>

.github/workflows/release.yml

@@ -17,6 +17,19 @@ jobs:
       - name: Check out code
         uses: actions/checkout@v3
 
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: "3.12"
+
+      - name: Install dependencies
+        run: |
+          pip install -r exporter/requirements.txt
+
+      - name: Run unit tests
+        run: |
+          python -m unittest exporter/test_exporter.py
+
       - name: Set up Helm
         uses: azure/setup-helm@v3
         with: