Use object equality when filtering rules in buildSchemaFromSDL

Similar in spirit to apollographql/apollo-server#3338.

The technique previously used for removing rules from the standard
`specifiedRules` was leveraging a check on `Function.prototype.name`, rather
than doing direct object equality.  While that does generally work, thanks
to the more recent standardization of `Function.prototype.name`, it still
breaks down under some of the more aggressive minification techniques since
a function's name is not guaranteed to remain the same.

Fixes: apollographql/apollo-server#3335

Author: abernix

packages/apollo-graphql/src/schema/buildSchemaFromSDL.ts

@@ -25,6 +25,13 @@ import { isDocumentNode, isNode } from "../utilities/graphql";
 import { GraphQLResolverMap } from "./resolverMap";
 import { GraphQLSchemaValidationError } from "./GraphQLSchemaValidationError";
 import { specifiedSDLRules } from "graphql/validation/specifiedRules";
+import {
+  KnownTypeNamesRule,
+  UniqueDirectivesPerLocationRule
+} from "graphql/validation";
+// Currently, this PossibleTypeExtensions rule is experimental and thus not
+// exposed directly from the rules module above. This may change in the future!
+import { PossibleTypeExtensions } from "graphql/validation/rules/PossibleTypeExtensions";
 import { mapValues, isNotNullOrUndefined } from "apollo-env";
 
 export interface GraphQLSchemaModule {
@@ -33,13 +40,13 @@ export interface GraphQLSchemaModule {
 }
 
 const skippedSDLRules = [
-  "PossibleTypeExtensions",
-  "KnownTypeNames",
-  "UniqueDirectivesPerLocation"
+  PossibleTypeExtensions,
+  KnownTypeNamesRule,
+  UniqueDirectivesPerLocationRule
 ];
 
 const sdlRules = specifiedSDLRules.filter(
-  rule => !skippedSDLRules.includes(rule.name)
+  rule => !skippedSDLRules.includes(rule)
 );
 
 export function modulesFromSDL(