CI: github: enable pool debugging by default

This enables DEBUG_MEMORY_POOLS and DEBUG_POOL_INTEGRITY so that by
default the tests run under stricter checks, which are likely to
catch more bugs. Note that these ones are permanently used in prod
on haproxy.org.
diff --git a/.github/workflows/vtest.yml b/.github/workflows/vtest.yml
index ac51605..a9e86b6 100644
--- a/.github/workflows/vtest.yml
+++ b/.github/workflows/vtest.yml
@@ -107,7 +107,7 @@
           ERR=1 \
           TARGET=${{ matrix.TARGET }} \
           CC=${{ matrix.CC }} \
-          DEBUG=-DDEBUG_STRICT=1 \
+          DEBUG="-DDEBUG_STRICT -DDEBUG_MEMORY_POOLS -DDEBUG_POOL_INTEGRITY" \
           ${{ join(matrix.FLAGS, ' ') }} \
           ADDLIB="-Wl,-rpath,/usr/local/lib/ -Wl,-rpath,$HOME/opt/lib/"
         sudo make install