Lazily init fetch dedupe cache

This module may be included in Pages Router where we don't actually dedupe fetch.

Since React.cache is cleared between requests anyway, initialising it when we patch fetch does not mean we cache less.
Unless we re-patch during requests which would probably be a bug anyway.

packages/next/src/server/lib/dedupe-fetch.ts

@@ -3,8 +3,6 @@
  */
 import * as React from 'react'
 
-// eslint-disable-next-line @typescript-eslint/no-unused-vars -- url is the cache key
-const getCacheEntries = React.cache((url: string): Array<any> => [])
 const simpleCacheKey = '["GET",[],null,"follow",null,null,null,null]' // generateCacheKey(new Request('https://blank'));
 
 function generateCacheKey(request: Request): string {
@@ -27,6 +25,9 @@ function generateCacheKey(request: Request): string {
 }
 
 export function createDedupeFetch(originalFetch: typeof fetch) {
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars -- url is the cache key
+  const getCacheEntries = React.cache((url: string): Array<any> => [])
+
   return function dedupeFetch(
     resource: URL | RequestInfo,
     options?: RequestInit