ci: add JDK 26 testing support

Add JDK 26 to build matrices in GitHub Actions workflows.
Update Bazel integration tests in sdk-platform-java to run on JDK 25 and 26 with Security Manager override.

BUG=b/481669998
TAG=agy
CONV=7b193e4d-38f8-450c-8475-0b9ae0d04507

Author: lqiu96

.github/workflows/ci.yaml

@@ -59,7 +59,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        java: [11, 17, 21, 25]
+        java: [11, 17, 21, 25, 26]
     steps:
     - name: Get current week within the year
       id: date
@@ -226,7 +226,7 @@ jobs:
       fail-fast: false
       matrix:
         package: ${{ fromJSON(needs.changes.outputs.packages) }}
-        java: [11, 17, 21, 25]
+        java: [11, 17, 21, 25, 26]
     steps:
     - name: Get current week within the year
       id: date

.github/workflows/google-auth-library-java-ci.yaml

@@ -42,7 +42,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        java: [11, 17, 21, 25]
+        java: [11, 17, 21, 25, 26]
     steps:
     - uses: actions/checkout@v4
     - uses: actions/setup-java@v4

.github/workflows/java-bigquery-jdbc-ci.yaml

@@ -49,7 +49,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        java: [11, 17, 21, 25]
+        java: [11, 17, 21, 25, 26]
     steps:
     - uses: actions/checkout@v4
     - uses: actions/setup-java@v4

.github/workflows/java-bigtable-ci.yaml

@@ -41,7 +41,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        java: [11, 17, 21, 25]
+        java: [11, 17, 21, 25, 26]
     steps:
     - uses: actions/checkout@v4
     - uses: actions/setup-java@v4

.github/workflows/java-firestore-ci.yaml

@@ -41,7 +41,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        java: [11, 17, 21, 25]
+        java: [11, 17, 21, 25, 26]
     steps:
     - uses: actions/checkout@v4
     - uses: actions/setup-java@v4

.github/workflows/java-pubsub-ci.yaml

@@ -41,7 +41,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        java: [11, 17, 21, 25]
+        java: [11, 17, 21, 25, 26]
     steps:
     - uses: actions/checkout@v4
     - uses: actions/setup-java@v4

.github/workflows/java-spanner-jdbc-ci.yaml

@@ -47,7 +47,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        java: [11, 17, 21, 25]
+        java: [11, 17, 21, 25, 26]
     steps:
     - uses: actions/checkout@v4
     - uses: actions/setup-java@v4

.github/workflows/java-storage-nio-ci.yaml

@@ -47,7 +47,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        java: [11, 17, 21, 25]
+        java: [11, 17, 21, 25, 26]
     steps:
     - uses: actions/checkout@v4
     - uses: actions/setup-java@v4

.github/workflows/sdk-platform-java-ci.yaml

@@ -26,7 +26,7 @@ jobs:
     name: sdk-platform-java units
     strategy:
       matrix:
-        java: [ 11, 17, 21, 25 ]
+        java: [ 11, 17, 21, 25, 26 ]
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-java@v4
@@ -164,16 +164,21 @@ jobs:
         run: |
           bazelisk --batch test //sdk-platform-java/test/integration/... --test_output=errors
 
-  bazel-25:  
+  # JDK 24+ permanently disables Security Manager. Bazel's default test runner tries to install it.
+  # We must explicitly disable this behavior using shouldInstallTestSecurityManager=false.
+  bazel-no-security-manager-jdk24-plus:  
     needs: filter
     if: ${{ needs.filter.outputs.library == 'true' }}
     runs-on: ubuntu-22.04
-    name: sdk-platform-java integration (25)
+    name: sdk-platform-java integration (JDK 24+)
+    strategy:
+      matrix:
+        java: [ 25, 26 ]
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-java@v4
         with:
-          java-version: 25
+          java-version: ${{ matrix.java }}
           distribution: temurin
           cache: maven
       - run: bazelisk version

.github/workflows/showcase.yaml

@@ -101,7 +101,7 @@ jobs:
     runs-on: ubuntu-22.04
     strategy:
       matrix:
-        java: [ 11, 17, 21, 25 ]
+        java: [ 11, 17, 21, 25, 26 ]
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-java@v4