Closes hotwired#743

The change in behavior can be traced back to [hotwired#412][].
When the overlap between the `LinkInterceptor` and the
`LinkClickObserver` were unified, the technique used by the
`LinkInterceptor` to prevent duplicate event handlers from responding to
the same `click` event was changed in a subtle way.

In its place, this commit changes the `LinkClickObserver` and
`FormSubmitObserver` to ignore `<a>` clicks and `<form>` submissions if
they're annotated with `[data-remote="true"]`.

To exercise these edge cases, this commit also adds a `ujs.html` fixture
file along with a `ujs_tests.ts` module to cover situations when
`@rails/ujs` and `@hotwired/turbo` co-exist.

[hotwired#412]: hotwired#412

This reverts commit 9bef653.

[comment]: hotwired#744 (comment)
[FormInterceptor]: https://github.com/hotwired/turbo/blob/v7.1.0/src/core/frames/form_interceptor.ts#L31