Remove almost all usages of BindingKey

A follow-up will remove the remaining usages, but I didn't want to make this CL even more unwieldy than it already is

RELNOTES=n/a

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=179929249
diff --git a/java/dagger/internal/codegen/MembersInjectionMethods.java b/java/dagger/internal/codegen/MembersInjectionMethods.java
index 3b785c9..9d40f48 100644
--- a/java/dagger/internal/codegen/MembersInjectionMethods.java
+++ b/java/dagger/internal/codegen/MembersInjectionMethods.java
@@ -16,7 +16,6 @@
 
 package dagger.internal.codegen;
 
-import static com.google.common.base.MoreObjects.firstNonNull;
 import static com.google.common.base.Preconditions.checkNotNull;
 import static com.squareup.javapoet.MethodSpec.methodBuilder;
 import static dagger.internal.codegen.Accessibility.isTypeAccessibleFrom;
@@ -71,11 +70,9 @@
   }
 
   private MethodSpec membersInjectionMethod(Key key) {
-    Binding binding =
-        firstNonNull(
-                graph.resolvedBindings().get(BindingKey.membersInjection(key)),
-                graph.resolvedBindings().get(BindingKey.contribution(key)))
-            .binding();
+    ResolvedBindings resolvedBindings =
+        graph.membersInjectionBindings().getOrDefault(key, graph.contributionBindings().get(key));
+    Binding binding = resolvedBindings.binding();
     TypeMirror keyType = binding.key().type();
     TypeMirror membersInjectedType =
         isTypeAccessibleFrom(keyType, generatedComponentModel.name().packageName())