Huge update to pbi-managger for 10.0

Welcome our new "pbifs" FUSE launcher. This will replace about a dozen "nullfs" mounts
used to create a virtual "PBI" container with a single fuse mount, which internally does
all the mapping required to create virtual /usr/local namespaces.

This update should hopefully also improve stability going forward
Remove some testing files
Add back in the check for nvidia-linux support
Cleanup some of the old locking fixes
Fix a bug, only mount pbifs a single time