Always _discover_all when finding a sub-handle

[ktbarrett]

Currently we opportunistically attempt to find a handle by name without first discovering sub-handles. This often does not work. We could instead add some logic such that if it fails, it _discover_alls and then tries again before failing.

[marlonjames]

#2079 added this to try and help with pseudo-region discovery, since the VPI iteration code was better at finding those.
The followup #2143 which added iteration fallback in child handle lookup by name for Icarus took it out. And now #3817 expanded the VPI fallback to all simulators.

I'm not opposed to it in theory, I just wonder if there are any cases where iterating using the ordered set of iterators in the GPI implementations would give a handle to a different object than when looked up by name directly.