Fixes#26085.
Adds a basic retry utility with some defaults, starts off with a 100ms
wait, then 250ms, then 500ms
I've applied the retry in the http client, reusing an existing function,
so this also applies to retrying downloads of deno binaries in `upgrade`
and `compile`. I can make a separate function that doesn't retry so this
doesn't affect `upgrade` and `compile`, but it seemed desirable to have
retries there too, so I left it in.
