ci: Use libMainThreadChecker to test if all functions run on the correct thread

Xcode provides a tool called the “Main Thread Checker” which verifies that UI APIs are being used from the correct thread

Author: pentamassiv

.github/workflows/integration.yml

@@ -78,3 +78,6 @@ jobs:
       - name: Run integration tests in release mode
         if: matrix.features != 'wayland' && matrix.features != 'libei' && matrix.features != 'libei,wayland,xdo,x11rb' # On Linux, the integration tests only work with X11 for now
         run: cargo test integration --release --no-default-features --features ${{ matrix.features }} -- --test-threads=1 --nocapture --include-ignored
+        env:
+          DYLD_INSERT_LIBRARIES: /Applications/Xcode.app/Contents/Developer/usr/lib/libMainThreadChecker.dylib
+          MTC_RESET_INSERT_LIBRARIES: 0