This is a part of https://github.com/neondatabase/neon/pull/2595.
It takes out switch to per tenant upload queue and changes to pageserver
startup sequence because these two are highly interleaved with each
other. I'm still not happy with the size of the diff, but splitting
it even more will probably consume even more time. Ideally we should
do it, but this patch isis already a step forward and should be
easier to get this patch in yet still quite difficult.
Mainly because of the size and fixes for existing concerns which
will extend the diff even further
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
795c3ca131