minor: make-pif speed up

[alpapan]

When using jbrowse make-pif --csi it takes a few minutes with most going into the sort|bgzip command

We could provide options to speed up

• sort: --tmpdir the tmp directory for sort (-T) (e.g. user could provide /dev/shm)
• sort: or a memory option --buffer-size 2G.
• bgzip: --threads (as not all sort implementations have a parallel option)

This is for @jbrowse/cli/2.15.1 linux-x64 node-v20.16.0