Notes:
- We can actually use a single Activity.java file for oculus/pico now
- We can unconditionally compile os_android.c on Android
- No need for including extra jars in build system
- Headset rendering is guaranteed synchronous now, no need to ref L
- Add an "android flavor" build setting to differentiate between oculus
and pico devices, since they both use OpenXR.
- Update the pico manifest to reflect their OpenXR sample
- Remove some OpenGL hacks that aren't necessary anymore
Add entrypoints, headset backend code, fill in the Activity, and
add various special cases to account for the asynchronous render loop,
lack of sRGB support, and OpenGL state resets.
- lovr.graphics.tock returns the latest value of the timer, or 0.
- Timers are not in the stats table anymore.
This is to prepare for an upcoming internal change that affects timers.
- Rename drawMode to topology in some places.
- Batch uses DrawCommand internally to simplify stuff.
- Do less work while flushing.
- Store global head/tail cursors instead of unused per-batch cursors.
Having a normal Canvas object that represents the backbuffer reduces
some indirection where we have to last-minute check if a Canvas is
set. It also means that all of the draw-related info that was _sometimes_
on the Canvas is now _always_ on the Canvas, which reduces the amount
of redundant information we need to provide for a draw call.
There may be some issues related to changing the width/height/stereo
of the default Canvas.