Add eBPF tutorial and monitoring scripts for GPU activity

- Introduced a comprehensive README.md detailing the use of eBPF for monitoring GPU activity through kernel tracepoints.
- Added bpftrace scripts for monitoring AMD GPU operations, including buffer object creation, command submission, and interrupts.
- Created a bpftrace script for tracking DRM GPU scheduler activity across all modern GPU drivers.
- Developed a bpftrace script to monitor display vertical blanking events for frame timing analysis.
- Implemented a bpftrace script for Intel i915 GPU activity, focusing on GEM object management, memory operations, and page faults.

.github/workflows/test-libbpf.yml

@@ -95,3 +95,19 @@ jobs:
     - name: test 45
       run: |
           make -C src/45-scx-nest
+
+    - name: test 46 xdp-pktgen
+      run: |
+          make -C src/46-xdp-test
+
+    - name: test features bpf_arena
+      run: |
+          make -C src/features/bpf_arena
+
+    - name: test features bpf_iters
+      run: |
+          make -C src/features/bpf_iters
+
+    - name: test features bpf_wq
+      run: |
+          make -C src/features/bpf_wq