feat: setup 3.15.x lts branch

Author: burkedavison

.github/release-please.yml

@@ -17,6 +17,13 @@ branches:
       - >-
         google-cloud-logging/src/main/java/com/google/cloud/logging/Instrumentation.java
     branch: 3.13.x
+  - bumpMinorPreMajor: true
+    handleGHRelease: true
+    releaseType: java-backport
+    extraFiles:
+      - >-
+        google-cloud-logging/src/main/java/com/google/cloud/logging/Instrumentation.java
+    branch: 3.15.x
 extraFiles:
   - >-
     google-cloud-logging/src/main/java/com/google/cloud/logging/Instrumentation.java

.github/sync-repo-settings.yaml

@@ -65,6 +65,22 @@ branchProtectionRules:
       - OwlBot Post Processor
       - 'Kokoro - Test: Java GraalVM Native Image'
       - 'Kokoro - Test: Java 17 GraalVM Native Image'
+  - pattern: 3.15.x
+    isAdminEnforced: true
+    requiredApprovingReviewCount: 1
+    requiresCodeOwnerReviews: true
+    requiresStrictStatusChecks: false
+    requiredStatusCheckContexts:
+      - dependencies (17)
+      - lint
+      - clirr
+      - units (8)
+      - units (11)
+      - 'Kokoro - Test: Integration'
+      - cla/google
+      - OwlBot Post Processor
+      - 'Kokoro - Test: Java GraalVM Native Image'
+      - 'Kokoro - Test: Java 17 GraalVM Native Image'
 permissionRules:
   - team: yoshi-admins
     permission: admin