chore: setup 2.19.x lts branch (#1535)

Author: zhumin8

.github/release-please.yml

@@ -30,3 +30,7 @@ branches:
     handleGHRelease: true
     releaseType: java-backport
     branch: 2.17.x
+  - bumpMinorPreMajor: true
+    handleGHRelease: true
+    releaseType: java-backport
+    branch: 2.19.x

.github/sync-repo-settings.yaml

@@ -170,6 +170,22 @@ branchProtectionRules:
       - 'Kokoro - Test: Java GraalVM Native Image'
       - 'Kokoro - Test: Java 17 GraalVM Native Image'
       - javadoc
+  - pattern: 2.19.x
+    isAdminEnforced: true
+    requiredApprovingReviewCount: 1
+    requiresCodeOwnerReviews: true
+    requiresStrictStatusChecks: false
+    requiredStatusCheckContexts:
+      - dependencies (17)
+      - lint
+      - clirr
+      - units (8)
+      - units (11)
+      - 'Kokoro - Test: Integration'
+      - cla/google
+      - 'Kokoro - Test: Java GraalVM Native Image'
+      - 'Kokoro - Test: Java 17 GraalVM Native Image'
+      - javadoc
 permissionRules:
   - team: yoshi-admins
     permission: admin