readline: eagerly load string_decoder

There was no point in lazy loading the string_decoder, since it
would be used in all cases anyway.

PR-URL: #30807
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/readline.js

@@ -55,8 +55,7 @@ const {
   kClearScreenDown
 } = CSI;
 
-// Lazy load StringDecoder for startup performance.
-let StringDecoder;
+const { StringDecoder } = require('string_decoder');
 
 // Lazy load Readable for startup performance.
 let Readable;
@@ -84,9 +83,6 @@ function Interface(input, output, completer, terminal) {
     return new Interface(input, output, completer, terminal);
   }
 
-  if (StringDecoder === undefined)
-    StringDecoder = require('string_decoder').StringDecoder;
-
   this._sawReturnAt = 0;
   this.isCompletionEnabled = true;
   this._sawKeyPress = false;
@@ -1122,8 +1118,6 @@ Interface.prototype[Symbol.asyncIterator] = function() {
 function emitKeypressEvents(stream, iface) {
   if (stream[KEYPRESS_DECODER]) return;
 
-  if (StringDecoder === undefined)
-    StringDecoder = require('string_decoder').StringDecoder;
   stream[KEYPRESS_DECODER] = new StringDecoder('utf8');
 
   stream[ESCAPE_DECODER] = emitKeys(stream);
@@ -1138,8 +1132,11 @@ function emitKeypressEvents(stream, iface) {
       if (r) {
         clearTimeout(timeoutId);
 
+        let escapeTimeout = ESCAPE_CODE_TIMEOUT;
+
         if (iface) {
           iface._sawKeyPress = r.length === 1;
+          escapeTimeout = iface.escapeCodeTimeout;
         }
 
         for (let i = 0; i < r.length; i++) {
@@ -1151,10 +1148,7 @@ function emitKeypressEvents(stream, iface) {
             stream[ESCAPE_DECODER].next(r[i]);
             // Escape letter at the tail position
             if (r[i] === kEscape && i + 1 === r.length) {
-              timeoutId = setTimeout(
-                escapeCodeTimeout,
-                iface ? iface.escapeCodeTimeout : ESCAPE_CODE_TIMEOUT
-              );
+              timeoutId = setTimeout(escapeCodeTimeout, escapeTimeout);
             }
           } catch (err) {
             // If the generator throws (it could happen in the `keypress`