[Quest/Go] Perf tweaking

[avaer]

We haven't done any perf measuring of the Oculus mobile case yet.

This issue is to do profiling and optimize some of the Oculus code paths. For example, multisample blitting and non-blitting back to the main framebuffer could do a lot on a memory bandwidth-constrained system like the Go.

[avaer]

The main blocker for continuing this is to get inspector support in the Android build, which is currently disabled in node-exokit.

We might ship that part directly with the move to Node 12.

The main thing we need to do is rebuild the libnode.a nodes for the mobile platforms to use the new Node 12 code, with a baked snapshot.

[avaer]

Major performance work happening here: #1071