ci(external-it): retry dependency build on transient mirror failures (#30604)

Parity with main (#30590): wrap the 'Build dependencies for
integration-tests' step (mvn install -am) in all three external-IT jobs
in a 3x retry so a transient artifact-fetch failure doesn't kill the job
before any test runs. Warn+sleep only when a retry follows; terminal
::error:: on final failure.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: mohityadav766

.github/workflows/java-playwright-external.yml

@@ -180,7 +180,16 @@ jobs:
       - name: Build dependencies for integration-tests
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-        run: mvn -DskipTests install -pl :openmetadata-integration-tests -am
+        run: |
+          for attempt in 1 2 3; do
+            mvn -DskipTests install -pl :openmetadata-integration-tests -am && exit 0
+            if [ "${attempt}" -lt 3 ]; then
+              echo "::warning::Build attempt ${attempt} failed (transient dependency-mirror error); retrying in 30s"
+              sleep 30
+            fi
+          done
+          echo "::error::Build failed after 3 attempts (dependency resolution)"
+          exit 1
 
       - name: Install Playwright browsers
         run: |
@@ -359,7 +368,16 @@ jobs:
       - name: Build dependencies for integration-tests
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-        run: mvn -DskipTests install -pl :openmetadata-integration-tests -am
+        run: |
+          for attempt in 1 2 3; do
+            mvn -DskipTests install -pl :openmetadata-integration-tests -am && exit 0
+            if [ "${attempt}" -lt 3 ]; then
+              echo "::warning::Build attempt ${attempt} failed (transient dependency-mirror error); retrying in 30s"
+              sleep 30
+            fi
+          done
+          echo "::error::Build failed after 3 attempts (dependency resolution)"
+          exit 1
 
       - name: Acquire admin JWT from external cluster
         env:
@@ -497,7 +515,16 @@ jobs:
       - name: Build dependencies for integration-tests
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-        run: mvn -DskipTests install -pl :openmetadata-integration-tests -am
+        run: |
+          for attempt in 1 2 3; do
+            mvn -DskipTests install -pl :openmetadata-integration-tests -am && exit 0
+            if [ "${attempt}" -lt 3 ]; then
+              echo "::warning::Build attempt ${attempt} failed (transient dependency-mirror error); retrying in 30s"
+              sleep 30
+            fi
+          done
+          echo "::error::Build failed after 3 attempts (dependency resolution)"
+          exit 1
 
       - name: Acquire admin JWT from external cluster
         env: