Validate Gradle task properties on test run

By default `validateTaskProperties` is added only to `check` task's
dependencies, so doesn't run on our CI.
We can run `check` instead of `test` on CI, but since developers are
not used to it, I believe it's better to make `test` tasks depend on
`validateTaskProperties`

libraries/tools/kotlin-gradle-plugin/build.gradle

@@ -122,6 +122,7 @@ artifacts {
 }
 
 test.executable = "${JDK_18}/bin/java"
+test.dependsOn(validateTaskProperties)
 
 validateTaskProperties.failOnWarning = true