Extract sdk registration code into function for reuse

Test: m nothing
Change-Id: I0d0e36324808831deb9a32f07ca3696125703873
diff --git a/sdk/testing.go b/sdk/testing.go
index 7a2540a..4e31b04 100644
--- a/sdk/testing.go
+++ b/sdk/testing.go
@@ -122,12 +122,8 @@
 	ctx.PostDepsMutators(apex.RegisterPostDepsMutators)
 
 	// from this package
-	ctx.RegisterModuleType("sdk", SdkModuleFactory)
-	ctx.RegisterModuleType("sdk_snapshot", SnapshotModuleFactory)
-	ctx.RegisterModuleType("module_exports", ModuleExportsFactory)
-	ctx.RegisterModuleType("module_exports_snapshot", ModuleExportsSnapshotsFactory)
-	ctx.PreDepsMutators(RegisterPreDepsMutators)
-	ctx.PostDepsMutators(RegisterPostDepsMutators)
+	registerModuleExportsBuildComponents(ctx)
+	registerSdkBuildComponents(ctx)
 
 	ctx.Register()