util: use let instead of var for util/inspect.js

PR-URL: #30399
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

lib/internal/util/inspect.js

@@ -1133,7 +1133,7 @@ function formatPrimitive(fn, value, ctx) {
 
 function formatNamespaceObject(ctx, value, recurseTimes, keys) {
  const output = new Array(keys.length);
- for (var i = 0; i < keys.length; i++) {
+ for (let i = 0; i < keys.length; i++) {
  try {
  output[i] = formatProperty(ctx, value, recurseTimes, keys[i],
  kObjectType);
@@ -1221,7 +1221,7 @@ function formatArray(ctx, value, recurseTimes) {
 
  const remaining = valLen - len;
  const output = [];
- for (var i = 0; i < len; i++) {
+ for (let i = 0; i < len; i++) {
  // Special handle sparse arrays.
  if (!hasOwnProperty(value, i)) {
  return formatSpecialArray(ctx, value, recurseTimes, len, output, i);
@@ -1297,7 +1297,7 @@ function formatSetIterInner(ctx, recurseTimes, entries, state) {
  const maxLength = Math.min(maxArrayLength, entries.length);
  let output = new Array(maxLength);
  ctx.indentationLvl += 2;
- for (var i = 0; i < maxLength; i++) {
+ for (let i = 0; i < maxLength; i++) {
  output[i] = formatValue(ctx, entries[i], recurseTimes);
  }
  ctx.indentationLvl -= 2;
@@ -1465,7 +1465,7 @@ function isBelowBreakLength(ctx, output, start, base) {
  let totalLength = output.length + start;
  if (totalLength + output.length > ctx.breakLength)
  return false;
- for (var i = 0; i < output.length; i++) {
+ for (let i = 0; i < output.length; i++) {
  if (ctx.colors) {
  totalLength += removeColors(output[i]).length;
  } else {
@@ -1579,7 +1579,7 @@ function formatWithOptions(inspectOptions, ...args) {
  let tempStr;
  let lastPos = 0;
 
- for (var i = 0; i < first.length - 1; i++) {
+ for (let i = 0; i < first.length - 1; i++) {
  if (first.charCodeAt(i) === 37) { // '%'
  const nextChar = first.charCodeAt(++i);
  if (a + 1 !== args.length) {