libfabric: Always install fabtests (#15081)

libfabric used to install fabtests only when installed
using --test. fabtests has tools that are useful on a
running system, so they should be installed always.

* Rewrote the build/install part to always install
  fabtests alongside libfabric.
* Updated a few fabtests resources.
* Updated the test related stuff. Works for most versions
  now.
* Include tcp and udp fabrics so that the test suite works.