Back/forward set the Nav Inspector back to pending (#95865)
A back/forward (history traversal) navigation should not be captured by
the Nav Inspector, because it's not the same as a regular navigation: it
reads the entire navigation from cache, rather than fetching new data.
It might be the case that data in the bfcache is missing for some
reason, but in the normal case all the data will be available and the
navigation will be instant. So that's how we should model it in the Nav
Inspector.
In the future we may want to update the Nav Inspector UI to show that
the current screen was the result of a back/forward navigation, but for
now we will just reset the Nav Inspector back to the pending ("Waiting
for navigation...") state.
Includes the regression tests from #95793.
Co-authored-by: Dan Abramov <dan.abramov@gmail.com>
