Remove ORTE project

Will be replaced by PRRTE. Ensure that OMPI and OPAL layers build
without reference to ORTE. Setup opal/pmix framework to be static.
Remove support for all PMI-1 and PMI-2 libraries. Add support for
"external" pmix component as well as internal v4 one.

remove orte: misc fixes

 - UCX fixes
 - VPATH issue
 - oshmem fixes
 - remove useless definition
 - Add PRRTE submodule
 - Get autogen.pl to traverse PRRTE submodule
 - Remove stale orcm reference
 - Configure embedded PRRTE
 - Correctly pass the prefix to PRRTE
 - Correctly set the OMPI_WANT_PRRTE am_conditional
 - Move prrte configuration to the end of OMPI's configure.ac
 - Make mpirun a symlink to prun, when available
 - Fix makedist with --no-orte/--no-prrte option
 - Add a `--no-prrte` option which is the same as the legacy
   `--no-orte` option.
 - Remove embedded PMIx tarball. Replace it with new submodule
   pointing to OpenPMIx master repo's master branch
 - Some cleanup in PRRTE integration and add config summary entry
 - Correctly set the hostname
 - Fix locality
 - Fix singleton operations
 - Fix support for "tune" and "am" options

Signed-off-by: Ralph Castain <rhc@pmix.org>
Signed-off-by: Gilles Gouaillardet <gilles@rist.or.jp>
Signed-off-by: Joshua Hursey <jhursey@us.ibm.com>