Rename OpenXRInterface.OpenXrSessionState to OpenXRInterface.SessionState

[dsnopek]

This is a follow-up to #107619 which was merged before we finished debating the name of this enum :-)

I'm not a fan of the existing name for a few reasons:

1. It uses a lower-case r in OpenXr, which we don't use anywhere else (except in the C# version of some things that are called OpenXR* on the C++ and GDScript side)
2. It's redundant - we don't need to say "OpenXR" again, because this is part of OpenXRInterface
3. It's inconsistent with the rest of the enums on OpenXRInterface, some of which also mirror enums from the OpenXR API (for example, OpenXRInterface.HandTrackedSource), but none of the other enums include the OpenXR* prefix

Perhaps if we started with this convention originally it could make sense, but adding this now doesn't fit in with what we already have

[Mickeon]

For clarity, I removed the documentation label as the changes to the docs are merely a consequence of the enum being changed.

Either way, I do approve the names being less redundant.

[akien-mga]

Makes sense to me. Maybe you can add the doc nitpicks from #107619 which were also missed before merging?

[dsnopek]

Maybe you can add the doc nitpicks from #107619 which were also missed before merging?

Sure! In my latest push, I've fixed the remaining docs notes from @AThousandShips on #107619

[devloglogan]

Nothing gained with the redundant naming, LGTM! 🙂

[BastiaanOlij]

As the one introducing the redundant naming, it was an attempt to set apart enums that are ours, and those we mirror from the OpenXR spec.

But since we haven't done so consistently, and there isn't much value in it one way or the other, it's not a hill I'm willing to die on.

Seeing most seem happy with just leaving the prefix out, I'm happy for this to be merged and I'll make similar changes to the spatial entities PR as suggested by David.

[Repiteo]

Thanks!