Inspect'ing a page should be provide more concise output

[sax]

When inspecting or debugging a page, the output should be much more concise than it currently is in the latest released version, specifically because it includes the entire conn, with its assigns.

Proposal:

iex> conn
...>.  |> Pages.visit("/")
...>   |> dbg()
Pages.Driver.Conn.visit(page, "/")

iex> conn
...>   |> Pages.visit("/live")
...>   |> dbg()
Pages.Driver.LiveView.visit(page, "/live")

[sax]

I just shipped the above on main. I feel like there may be some extra bits missing, though...

• What should happen when there is extra context saved on the page? This is only tracked in the API at the top-level Pages.visit/3; drivers do not know anything about contexts.
• Is it important to know that a page is a live view vs a conn? Seems important?

[sax]

One place where tests automatically inspect the driver is when inspecting a page for a 404 response, in which case the concise inspect output drops the relevant information.

These were always difficult to debug, because the 404 status was deeply buried in the conn inspect, but we should at least try to provide enough info to help rather than hinder users.

[sax]

Thinking about it more, the reason the page is inspected for a 404 response is because Pages crashes on to_string/1 when the status code is not 200, which seems more like a bug than a feature. It should be possible to use Pages to test that a URL returns a 404 response without crashing.

Edited: Releasing v3.4.0 which allows a conn page to be stringified with any HTTP status code.