Convert robolectric_test's module-info.json to song

This produces this diff, which I beleive is beneign:
https://paste.googleplex.com/4846726910050304

Bug: 389720048
Test: diff'd module-info.json
Change-Id: I531644d208a0a9d0fb2166d158f77e671554e5d8
diff --git a/java/java.go b/java/java.go
index 66550d5..a5e1be7 100644
--- a/java/java.go
+++ b/java/java.go
@@ -1070,6 +1070,10 @@
 
 	setOutputFiles(ctx, j.Module)
 
+	j.javaLibraryModuleInfoJSON(ctx)
+}
+
+func (j *Library) javaLibraryModuleInfoJSON(ctx android.ModuleContext) *android.ModuleInfoJSON {
 	moduleInfoJSON := ctx.ModuleInfoJSON()
 	moduleInfoJSON.Class = []string{"JAVA_LIBRARIES"}
 	if j.implementationAndResourcesJar != nil {
@@ -1092,6 +1096,7 @@
 		moduleInfoJSON.Disabled = true
 		j.dexpreopter.ModuleInfoJSONForApex(ctx)
 	}
+	return moduleInfoJSON
 }
 
 func (j *Library) getJarInstallDir(ctx android.ModuleContext) android.InstallPath {