CMP0022: Plain target_link_libraries must populate link interface

The CMP0022 NEW behavior is that the INTERFACE_LINK_LIBRARIES property
exactly defines the link interface.  The plain target_link_libraries
signature says linking is transitive by default, so it should populate
the property.

This fixes a regression in 2.8.12.0 that caused target_link_libraries
to not implement transitive linking in the plain signature once the
policy CMP0022 is set to NEW.
CMP0022: Add test for target_link_libraries plain signature
Merge branch 'handle-only-plain-tll' into next