GitHub docs have been moved around once again.

I recently found out they aren't required,
and for simple steps which can be stringified easily,
they are rather pointless and verbose.

It turns out that the globbing used by actions/cache does not actually
support reading env vars, and so the caching of GOCACHE on windows never
worked. Use the full path relative to $HOME.

We also start suggesting the inclusion of the Go version as part of the
cache key, because GOCACHE is different per go version.

Finally, bump the versions of setup-go and checkout.

While here, drop the FAQ about module support,
as it's already been the default for over a year,
and has been a default for a long time if a go.mod file exists.

A recent change upgraded us to setup-go@v4,
but failed to keep the "test" job without the use of any caching.
Rename it to keep that clear.

* Add a line about the token generated in the workflow
* Hardcode a user and provide an explanation as it is not used by GitHub

"Environment reference" got removed in favor of other pages.
The forum to report bugs has been closed for some time.
The caveat about %TEMP% was removed as a "won't fix" issue.

And the link just contributed by someone else was in French.

It has been obsolete for half a decade, and noone uses them anymore.

GitHub loves moving these pages around with redirects.