Change logtape/tuplestore code to use int64 for block numbers

Change logtape/tuplestore code to use int64 for block numbers

The code previously relied on "long" as type to track block numbers,
which would be 4 bytes in all Windows builds or any 32-bit builds.  This
limited the code to be able to handle up to 16TB of data with the
default block size of 8kB, like during a CLUSTER.  This code now relies
on a more portable int64, which should be more than enough for at least
the next 20 years to come.

This issue has been reported back in 2017, but nothing was done about it
back then, so here we go now.

Reported-by: Peter Geoghegan
Reviewed-by: Heikki Linnakangas
Discussion: https://postgr.es/m/CAH2-WznCscXnWmnj=STC0aSa7QG+BRedDnZsP=Jo_R9GUZvUrg@mail.gmail.com