Harmonize CI configuration

This commit harmonizes our CI configuration with Spring Boot, in
particular the clever use of reusable custom actions that simplify
the workflow definition quite a bit.

One main difference compared to Spring Boot is that we can now
specify a different distribution for a Java version to test, in
preparation for the support of building against 23-ea

See gh-32090

.github/workflows/validate-gradle-wrapper.yml

@@ -0,0 +1,11 @@
+name: "Validate Gradle Wrapper"
+on: [push, pull_request]
+permissions:
+  contents: read
+jobs:
+  validation:
+    name: "Validate Gradle Wrapper"
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: gradle/actions/wrapper-validation@dbbdc275be76ac10734476cc723d82dfe7ec6eda # v3.4.2