Make DependencyRequest.Kind a top-level, exposed type (RequestKind) in dagger.model

RELNOTES=n/a

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=179205348
diff --git a/java/dagger/internal/codegen/ProducerFromProviderFieldInitializer.java b/java/dagger/internal/codegen/ProducerFromProviderFieldInitializer.java
index fae83ac..0b3c9e6 100644
--- a/java/dagger/internal/codegen/ProducerFromProviderFieldInitializer.java
+++ b/java/dagger/internal/codegen/ProducerFromProviderFieldInitializer.java
@@ -21,6 +21,7 @@
 
 import com.squareup.javapoet.ClassName;
 import com.squareup.javapoet.CodeBlock;
+import dagger.model.RequestKind;
 import dagger.producers.Producer;
 import java.util.Optional;
 
@@ -43,7 +44,7 @@
   @Override
   protected CodeBlock getFieldInitialization() {
     return FrameworkType.PROVIDER.to(
-        DependencyRequest.Kind.PRODUCER,
+        RequestKind.PRODUCER,
         componentBindingExpressions
             .getDependencyExpression(
                 FrameworkDependency.create(resolvedBindings.bindingKey(), PROVISION),