test(s3tables): add Dremio Iceberg catalog integration tests

Add comprehensive integration tests for Dremio with SeaweedFS's Iceberg
REST Catalog, following the same patterns as existing Spark and Trino tests.

Tests include:
- Basic catalog connectivity and schema operations
- Table creation, insertion, and querying (CRUD)
- Deterministic table location specification
- Multi-level namespace support

Implementation includes:
- dremio_catalog_test.go: Core test environment and basic operations
- dremio_crud_operations_test.go: Schema and table CRUD testing
- dremio_deterministic_location_test.go: Location and namespace testing
- Comprehensive README and implementation documentation

CI/CD:
- Added dremio-iceberg-catalog-tests job to s3-tables-tests.yml
- Pre-pulls Dremio image, runs with 25m timeout
- Uploads artifacts on failure

.github/workflows/s3-tables-tests.yml

@@ -194,6 +194,72 @@ jobs:
           path: test/s3tables/catalog_trino/test-output.log
           retention-days: 3
 
+  dremio-iceberg-catalog-tests:
+    name: Dremio Iceberg Catalog Integration Tests
+    runs-on: ubuntu-22.04
+    timeout-minutes: 30
+
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v6
+
+      - name: Set up Go
+        uses: actions/setup-go@v6
+        with:
+          go-version-file: 'go.mod'
+        id: go
+
+      - name: Set up Docker
+        uses: docker/setup-buildx-action@v4
+
+      - name: Pre-pull Dremio image
+        run: docker pull dremio/dremio:latest
+
+      - name: Run go mod tidy
+        run: go mod tidy
+
+      - name: Install SeaweedFS
+        run: |
+          go install -buildvcs=false ./weed
+
+      - name: Run Dremio Iceberg Catalog Integration Tests
+        timeout-minutes: 25
+        working-directory: test/s3tables/catalog_dremio
+        run: |
+          set -x
+          set -o pipefail
+          echo "=== System Information ==="
+          uname -a
+          free -h
+          df -h
+          echo "=== Starting Dremio Iceberg Catalog Tests ==="
+
+          # Run Dremio + Iceberg catalog integration tests
+          go test -v -timeout 20m . 2>&1 | tee test-output.log || {
+            echo "Dremio Iceberg catalog integration tests failed"
+            exit 1
+          }
+
+      - name: Show test output on failure
+        if: failure()
+        working-directory: test/s3tables/catalog_dremio
+        run: |
+          echo "=== Test Output ==="
+          if [ -f test-output.log ]; then
+            tail -200 test-output.log
+          fi
+
+          echo "=== Process information ==="
+          ps aux | grep -E "(weed|test|docker)" || true
+
+      - name: Upload test logs on failure
+        if: failure()
+        uses: actions/upload-artifact@v7
+        with:
+          name: dremio-iceberg-catalog-test-logs
+          path: test/s3tables/catalog_dremio/test-output.log
+          retention-days: 3
+
   polaris-integration-tests:
     name: Polaris Integration Tests
     runs-on: ubuntu-22.04