`mtkcompile` with inputs requires toggling namespacing off

[AayushSabharwal]

mtkcompile requires that the inputs passed to it via the inputs kwarg are not namespaced with the top-level system. However, the trivial user workflow is

@named sys = MyModel()
sysRed = mtkcompile(sys; inputs = [sys.var, sys.other_var])

Which causes sys.var and sys.other_var to be namespaced. This can be worked around by doing

@named sys = MyModel()
sys = toggle_namespacing(sys, false)
sysRed = mtkcompile(sys; inputs = [sys.var, sys.other_var])

But that isn't the nicest UX.