[metacling] More tests for template func def inst:
[metacling] More tests for template func def inst:

Template parameter packs can be empty; template template args should work.

olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root