http2: reduce require calls in http2/core

This commit removes unnecesary requires of http and internal/util in
http2/core.js
Backport-PR-URL: #22850
PR-URL: #20422
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

Author: danbev

lib/internal/http2/core.js

@@ -23,9 +23,12 @@ const { onServerStream,
  Http2ServerResponse,
 }=require('internal/http2/compat');
 const{ utcDate }=require('internal/http');
-const{ promisify }=require('internal/util');
+const{
+ promisify,
+customInspectSymbol: kInspect
+}=require('internal/util');
 const{ isArrayBufferView }=require('internal/util/types');
-const{_connectionListener: httpConnectionListener}=require('http');
+const{_connectionListener: httpConnectionListener}=http;
 const{ createPromise, promiseResolve }=process.binding('util');
 constdebug=util.debuglog('http2');
 
@@ -67,7 +70,6 @@ const { constants, nameForErrorCode } = binding;
 constNETServer=net.Server;
 constTLSServer=tls.Server;
 
-constkInspect=require('internal/util').customInspectSymbol;
 const{ kIncomingMessage }=require('_http_common');
 const{ kServerResponse }=require('_http_server');