CI: Enable PAX module in Coverity scan workflow

The PAX storage module was missing from the daily Coverity static analysis
scan, which left potential code issues undetected. This change ensures PAX
module is properly initialized and included in the scan process, providing
better code quality coverage for the entire project.

Changes made:
- Added `git submodule update --init` command before configure
- Added `--enable-pax` flag to configure options

Before this PR, the Coverity scan had errors because of the PAX feature
is introduced.

See: #1049

Author: tuhaihe

.github/workflows/coverity.yml

@@ -90,12 +90,14 @@ jobs:
         su - gpadmin -c "cd $WORKSPACE"
         export LD_LIBRARY_PATH=/usr/local/cloudberry-db/lib:LD_LIBRARY_PATH
         export PATH=$WORKSPACE/coverity_tool/bin:$PATH
+        git submodule update --init
         ./configure --prefix=/usr/local/cloudberry-db \
             --disable-external-fts \
             --enable-gpcloud \
             --enable-ic-proxy \
             --enable-orafce \
             --enable-orca \
+            --enable-pax \
             --enable-pxf \
             --enable-tap-tests \
             --with-gssapi \
@@ -122,4 +124,4 @@ jobs:
           --form file=@cov.tar.gz \
           --form version="Commit $GITHUB_SHA" \
           --form description="Build submitted via CI" \
-          https://scan.coverity.com/builds?project=apache%2Fcloudberry
+          https://scan.coverity.com/builds?project=apache%2Fcloudberry