util,assert: expose util.isDeepStrictEqual()

Provide `util.isDeepStrictEqual()` that works like
`assert.deepStrictEqual()` but returns a boolean rather than throwing an
error.

Several userland modules have needed this functionality and implemented
it independently. This functionality already exists in Node.js core, so
this exposes it for use by modules. Modules that have needed this
functionality include `lodash`, `concordance` (used by `ava`), and
`qunit`.

PR-URL: nodejs/node#16084
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

doc/api/assert.md

@@ -134,7 +134,7 @@ changes:
 * `expected` {any}
 * `message` {any}
 
-Similar to `assert.deepEqual()` with the following exceptions:
+Identical to [`assert.deepEqual()`][] with the following exceptions:
 
 1. Primitive values besides `NaN` are compared using the [Strict Equality
    Comparison][] ( `===` ). Set and Map values, Map keys and `NaN` are compared

doc/api/util.md

@@ -455,6 +455,21 @@ util.inspect.defaultOptions.maxArrayLength = null;
 console.log(arr); // logs the full array
 ```
 
+## util.isDeepStrictEqual(val1, val2)
+<!-- YAML
+added: REPLACEME
+-->
+
+* `val1` {any}
+* `val2` {any}
+* Returns: {string}
+
+Returns `true` if there is deep strict equality between `val` and `val2`.
+Otherwise, returns `false`.
+
+See [`assert.deepStrictEqual()`][] for more information about deep strict
+equality.
+
 ## util.promisify(original)
 <!-- YAML
 added: v8.0.0
@@ -1187,6 +1202,7 @@ Deprecated predecessor of `console.log`.
 [`Buffer.isBuffer()`]: buffer.html#buffer_class_method_buffer_isbuffer_obj
 [`Error`]: errors.html#errors_class_error
 [`Object.assign()`]: https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Object/assign
+[`assert.deepStrictEqual()`]: assert.html#assert_assert_deepstrictequal_actual_expected_message
 [`console.error()`]: console.html#console_console_error_data_args
 [`console.log()`]: console.html#console_console_log_data_args
 [`util.inspect()`]: #util_util_inspect_object_options