FIX: remove check that triggered NotImplementedException for Usage bindings (ISXB-373)

[jamesmcgill]

Description

If a Usage (e.g. Submit) was bound then an NotImplemented exception could occur because it hit a case that wasn't implemented yet.

• The sample project I had was extremely simple to reproduce: just bind an action to Submit (then attempt to call InputControlPath::ToHumanReadableString() to trigger the failure).
• In that case the control will be Key/Enter and control.device will be Keyboard.
• Usages are stored at device level, not in the control subhierarchy AFAIK.

There is a TODO: support scavenging a subhierarchy for usages there, so my first instinct was to implement the missing case, however, at least in this case I couldn't see why we would want to search from Key/Enter downwards in the subhierarchy. And I couldn't come up with another use-case. I'm also unsure how this could be implemented if we wanted to (without moving usages out to be on per control basis which seems redundant?).

Perhaps I haven't understood the intention of the comment correctly, so happy to hear if someone knows better?

Even if we do have future plans for this, I think we should still remove this Exception today as the reproduction was extremely easy to trigger and I don't see any issue with looking at the root device for Usages in the meantime.

Changes made

• Removed the check that triggered the exception and allow the code to fall through and use the device.

Checklist

Before review:

• Changelog entry added.
  • Explains the change in Changed, Fixed, Added sections.
  • For API change contains an example snippet and/or migration example.
  • FogBugz ticket attached, example ([case %number%](https://issuetracker.unity3d.com/issues/...)).
  • FogBugz is marked as "Resolved" with next release version correctly set.
• Tests added/changed, if applicable.
  • Functional tests Area_CanDoX, Area_CanDoX_EvenIfYIsTheCase, Area_WhenIDoX_AndYHappens_ThisIsTheResult.
  • Performance tests.
  • Integration tests.
• Docs for new/changed API's.
  • Xmldoc cross references are set correctly.
  • Added explanation how the API works.
  • Usage code examples added.
  • The manual is updated, if needed.

During merge:

• Commit message for squash-merge is prefixed with one of the list:
  • NEW: ___.
  • FIX: ___.
  • DOCS: ___.
  • CHANGE: ___.
  • RELEASE: 1.1.0-preview.3.

[lyndon-unity]

I don't understand this area well enough to understand side effects but I feel that removing this exception is reasonable.

Perhaps a debug warning could be valuable but I'm comfortable clicking approve for the error case reported.

[jamesmcgill]

Yeah, I'm also not 100% on what is intended missing feature here. Unless there is a rush to get this in, I think we can leave it open for the others to review incase I'm missing something.

I don't even think the warning is necessary, as my understanding at the moment is that this works as-is (i.e. continues to use the device when looking for the Usage in this case should be correct).

[jimon]

I couldn't came up with counter example. Given that nobody complained for years about this lets merge and see what breaks down the line.