Enable JUnitPlatform for Spock tests (#4568)

Since Spock 2 is based on the JUnit platform, Gradle needs to be configured explicitly to discover and run the tests.
Also, since HikariCP 5 requires JDK 11+, we have to switch back to 4.0.3.

modules/spock/build.gradle

@@ -12,7 +12,7 @@ dependencies {
     testImplementation project(':mysql')
     testImplementation project(':postgresql')
 
-    testImplementation 'com.zaxxer:HikariCP:5.0.0'
+    testImplementation 'com.zaxxer:HikariCP:4.0.3'
     testImplementation 'org.apache.httpcomponents:httpclient:4.5.13'
 
     testRuntimeOnly 'org.postgresql:postgresql:42.2.24'
@@ -26,3 +26,10 @@ sourceJar {
        allSource contains both .java and .groovy files */
     from sourceSets.main.allSource
 }
+
+test {
+    useJUnitPlatform()
+    testLogging {
+        events "passed", "skipped", "failed"
+    }
+}