Dynamically load libfuse2/3

[jamesbornholt]

Since fuser only uses libfuse for mount/unmount, we should be able to load the right one dynamically rather than choosing at compile time. This will be useful because AL2 is still on libfuse2 whereas most other distros have moved on to libfuse3.

Right now at compile time fuser includes only the code for the version it compiles with. We should just include both and dynamically dispatch the mount/unmount/communications.

[dannycjones]

@jamesbornholt do you believe this will require changes within the fuser crate, or its feasible without changing it?

[jamesbornholt]

It's exclusively fuser changes, we can't/shouldn't do it on our side.