test.py: Run the two-console ad hoc tests in relay and P2P mode, and in CI

The pair tests that pass go in tests_good, and each runs twice: through
the built-in server's relay and P2P. pair_known_failures lists the ones
that fail in only one mode. A P2P test that needs a loopback address
the machine lacks (macOS has only 127.0.0.1) is skipped with a warning,
and the run fails at the end with the command that adds it. The macOS
CI runners add 127.0.0.2. Each run gets a random port offset.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/build.yml

@@ -550,6 +550,12 @@ jobs:
       timeout-minutes: 30
       run: build/PPSSPPUnitTest ALL
 
+    # The two-console ad hoc tests run in P2P too, where instance N binds to 127.0.0.N. Linux and
+    # Windows route all of 127/8 to the loopback; macOS needs the address added.
+    - name: Add a loopback address for the P2P ad hoc tests
+      if: matrix.extra == 'test' && runner.os == 'macOS'
+      run: sudo ifconfig lo0 alias 127.0.0.2 up
+
     - name: Execute headless tests
       if: matrix.extra == 'test' && runner.os != 'Linux'
       timeout-minutes: 30