MINOR: cleanTest ought to remove output of unitTest task and integrat… (#10585)

The command used by our private CI is ./gradlew cleanTest xxx:test. It does not re-run test when we use unitTest and integrationTest to replace test. The root cause is that we don't offer test output (unitTest and integrationTest) to cleanTest task and so it does not delete related test output.

Reviewers: Ismael Juma <ismael@juma.me.uk>

build.gradle

@@ -449,6 +449,14 @@ subprojects {
     }
   }
 
+  // remove test output from all test types
+  tasks.withType(Test).all { t ->
+    cleanTest {
+      delete t.reports.junitXml.destination
+      delete t.reports.html.destination
+    }
+  }
+
   jar {
     from "$rootDir/LICENSE"
     from "$rootDir/NOTICE"