util: add coverage for util.inspect.colors alias setter

Add test to confirm that the setter for aliases in `util.inspect.colors`
keeps the alias reference-equal to the target value.

Refs: https://coverage.nodejs.org/coverage-5b0308cd823a5110/lib/internal/util/inspect.js.html#L357
Refs: https://codecov.io/gh/nodejs/node/src/5b0308cd823a511098dadf9ddd5a35e3a9dbb424/lib/internal/util/inspect.js#L357

PR-URL: #31743
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

test/parallel/test-util-inspect.js

@@ -2724,3 +2724,28 @@ assert.strictEqual(
       '\x1B[2mdef: \x1B[33m5\x1B[39m\x1B[22m }'
   );
 }
+
+// Test changing util.inspect.colors colors and aliases.
+{
+  const colors = util.inspect.colors;
+
+  const originalValue = colors.gray;
+
+  // "grey" is reference-equal alias of "gray".
+  assert.strictEqual(colors.grey, colors.gray);
+
+  // Assigninging one should assign the other. This tests that the alias setter
+  // function keeps things reference-equal.
+  colors.gray = [0, 0];
+  assert.deepStrictEqual(colors.gray, [0, 0]);
+  assert.strictEqual(colors.grey, colors.gray);
+
+  colors.grey = [1, 1];
+  assert.deepStrictEqual(colors.grey, [1, 1]);
+  assert.strictEqual(colors.grey, colors.gray);
+
+  // Restore original value to avoid side effects in other tests.
+  colors.gray = originalValue;
+  assert.deepStrictEqual(colors.gray, originalValue);
+  assert.strictEqual(colors.grey, colors.gray);
+}