[dart:js_interop] Reach (mostly) parity with js_util

https://github.com/dart-lang/sdk/issues/54004

In order to reach parity with js_util, we expose operators
through an extension and do some partial renames in order
to make the member names sound better e.g. `equals` instead
of `equal`. We also expose the following from js_util:

- NullRejectionException

We don't expose `isJavaScriptArray` and `isJavaScriptSimpleObject`
as they can expressed through other forms of interop. There
was an esoteric bug where we needed these members for Firefox
in pkg:test, but the package no longer uses these members, so to
avoid increasing the API space too much, we do not export them.

For the same reason, we also don't expose `objectGetPrototypeOf`,
`objectPrototype`, `objectKeys`.

We don't expose `allowInteropCaptureThis` as it will take some
work to handle this in dart2wasm. That work is tracked in
https://github.com/dart-lang/sdk/issues/54381.

Lastly, `instanceof` and `instanceOfString` is moved to be on
`JSAny?`, as this operator is useful to avoid needing to
downcast to `JSObject` e.g. `any.instanceOfString('Window')`
instead of `any.typeofEquals('object') &&
(any as JSObject).instanceOfString('Window')`.

Extensions are reorganized and renamed to handle these changes.

CoreLibraryReviewExempt: Backend-specific library.
Change-Id: Ib1a7fabc3fa985ef6638620becccd27eeca68c25
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/341140
Reviewed-by: Sigmund Cherem <sigmund@google.com>