refactor(core): Clean up dependencies (spinnaker#589)

In preparation for a kork bump that will change some dependencies
from api to implementation, add explicit dependencies where
required.

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

build.gradle

@@ -24,6 +24,7 @@ allprojects {
   group = "com.netflix.spinnaker.rosco"
 
   if (name != "rosco-bom") {
+    apply plugin: 'java-library'
     apply plugin: "groovy"
 
     dependencies {

rosco-core/rosco-core.gradle

@@ -2,8 +2,10 @@ dependencies {
   compileOnly "org.projectlombok:lombok"
   annotationProcessor "org.projectlombok:lombok"
 
+  api "com.netflix.spinnaker.kork:kork-artifacts"
+  api "org.codehaus.groovy:groovy"
+
   implementation "com.netflix.frigga:frigga"
-  implementation "com.netflix.spinnaker.kork:kork-artifacts"
   implementation "com.netflix.spinnaker.kork:kork-jedis"
   implementation "com.netflix.spinnaker.kork:kork-swagger"
   implementation "com.netflix.spinnaker.kork:kork-web"