GEODE-5688 Create task to generate all sources for better IDE behavior (

apache#2422)



Use `./gradlew generate` to create the sources from both protobuf and
ANTLR, then refresh the IDE sources and build as normal.

build.gradle

@@ -100,3 +100,8 @@ task devBuild(dependsOn: [":assemble"]) {
     }
   }
 }
+
+task generate() {
+  group = 'Build'
+  description = "Top-level target for all source generation. Helps IDE integration"
+}

geode-core/build.gradle

@@ -302,3 +302,5 @@ distributedTest {
   // Some tests have inner tests that should be ignored
   exclude "**/*\$*.class"
 }
+
+rootProject.generate.dependsOn(generateGrammarSource)

geode-protobuf-messages/build.gradle

@@ -61,3 +61,7 @@ task zip(type: Zip) {
 }
 
 assemble.dependsOn 'zip'
+
+afterEvaluate {
+  rootProject.generate.dependsOn(generateProto)
+}