Revert "Extract TypeScript utility types to apollo-server-env (#2415)"

This reverts commit 3a3c67d.

Revert this and #2417 on release-2.5.0 because having apollo-server-plugin-base
use newly added types from apollo-server-env yet only declare it as a
devDependency meant that TypeScript consumers of the published alpha packages
could end up breaking because the import of apollo-server-env could be resolved
to an older version of the package without the newly added types.

I'm not sure if this reversion is the right long term answer vs making the
apollo-server-env dependency non-dev, but this will let the alpha process for
2.5.0 move forward for now.

packages/apollo-datasource-rest/src/RESTDataSource.ts

@@ -7,7 +7,6 @@ import {
   URL,
   URLSearchParams,
   URLSearchParamsInit,
-  ValueOrPromise,
 } from 'apollo-server-env';
 
 import { DataSource, DataSourceConfig } from 'apollo-datasource';
@@ -42,6 +41,8 @@ export interface CacheOptions {
 export type Body = BodyInit | object;
 export { Request };
 
+type ValueOrPromise<T> = T | Promise<T>;
+
 export abstract class RESTDataSource<TContext = any> extends DataSource {
   httpCache!: HTTPCache;
   context!: TContext;

packages/apollo-server-env/src/index.d.ts

@@ -1,3 +1,2 @@
 export * from './fetch';
 export * from './url';
-export * from './typescript-utility-types';

packages/apollo-server-plugin-base/src/index.ts

@@ -1,5 +1,3 @@
-import { ValueOrPromise, WithRequired } from 'apollo-server-env';
-export { WithRequired };
 import {
   GraphQLServiceContext,
   GraphQLRequestContext,
@@ -13,13 +11,17 @@ export {
   GraphQLResponse,
 };
 
+type ValueOrPromise<T> = T | Promise<T>;
+
 export interface ApolloServerPlugin {
   serverWillStart?(service: GraphQLServiceContext): ValueOrPromise<void>;
   requestDidStart?<TContext>(
     requestContext: GraphQLRequestContext<TContext>,
   ): GraphQLRequestListener<TContext> | void;
 }
 
+export type WithRequired<T, K extends keyof T> = T & Required<Pick<T, K>>;
+
 export interface GraphQLRequestListener<TContext = Record<string, any>> {
   parsingDidStart?(
     requestContext: WithRequired<