Java callbacks are now directly dispatched to their handler, instead
of first going through filament's opportunistic dispatch, reducing
callback latency.
deprecate Stream::stream(intptr_t).
This method was needed for ARCore back in the days, but there is now a
zero-copy way to achieve the same thing. This API shouldn't be used anymore.
Previously, Streams had two modes (native and texid), this adds a third
mode called "acquired", which allows for copy-free synchronized external
textures in OpenGL and paves the way for Vulkan.
The native mode is now deprecated but texid mode needs to stay around
until all clients can be upgraded.
In an early prototype, this functionality was added directly into
Texture but required quite a bit of additional state tracking, so the
Stream API seemed like a better fit.
This API is probably not necessary for Metal due to Metal's shared
ownership semantics.
This has been tested with a new Android sample that will be added in a
subsequent PR.
No need for a proper library, this is just a common location to simplify
JNI bindings in other projects like filamat and gltfio.
There is no need to move the one Java source file (`NioUtils.java`)
since downstream libraries will have a dependency on Filament, and
FindClass should work fine.
In this first step, we just "blindly" move everything under src/driver
to a new library libbackend.a. And all headers are moved under
private/backend.
Note that "driver" is renamed "backend", but namespaces are unchanged for now.
Later we'll have to untangle the actual private headers from public
ones and ideally not have any private headers.
