BaseTools/Plugin: Add HostBasedUnitTestRunner plugin

BaseTools/Plugin: Add HostBasedUnitTestRunner plugin

https://bugzilla.tianocore.org/show_bug.cgi?id=2505

Add plugin to BaseTools to run host based unit tests.

Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Bret Barkelew <Bret.Barkelew@microsoft.com>
Acked-by: Bob Feng <bob.c.feng@intel.com>