[Bullet] Raycasts sometimes go through convex shapes and hit the far side when BT_USE_DOUBLE_PRECISION is enabled.

[jitspoe]

Godot version: 3.2.2.rc.custom_build.d69b856a4

OS/device including version: Windows 8.1

Issue description:
Had precision issues with bullet collision detection, so I compiled with BT_USE_DOUBLE_PRECISION defined. That improved the kinematic collision issues, but made raycasts sometimes go through the front surface of convex collision. I also created an issue on the bullet github in case it's an issue with the library: bulletphysics/bullet3#2949

Here the raycast is coming from the right and goes through the convex collision. Green line points to collision location. Cyan line is the normal.

With double precision disabled:

Steps to reproduce:
Define BT_USE_DOUBLE_PRECISION in scons, compile, and try raycasting against a convex shape (can be as simple as a box, but not an actual "box shape" shape) from different angles. Some will go through.
env_base.Append(CPPDEFINES=["BT_USE_DOUBLE_PRECISION"]) in SConstruct file.

Minimal reproduction project:

Test Double Precision Raycast.zip

Here's a build of the engine with double precision enabled:
godot.windows.opt.tools.32_double_precision_bullet.zip

[jitspoe]

It SEEMS like adding btResult.m_flags |= btTriangleRaycastCallback::kF_UseGjkConvexCastRaytest; to BulletPhysicsDirectSpaceState::intersect_ray() may fix the issue. Haven't tested how that behaves with double precision off, though. I think we want to have double precision enabled unless there's some sort of performance issues with it. It has significantly improved the kinematic collision accuracy.