[3.x] CPUParticles2D - Add ability to follow physics interpolated target

[lawnjelly]

Allows a non-interpolated particle system to closely follow an interpolated target without tracking ahead of the target, by performing fixed timestep interpolation on the particle system global transform, and using this for emission.

Changes the default physics interpolation mode of CPUParticles2D to OFF, as in most cases this looks much better and mimics the behaviour of particles simulating every frame when physics interpolation is not in use.

Witness particles now look excellent even at low physics tick rates, here it is 3 physics ticks per second! 😮

2023-08-23.17-26-28.mp4

Notes

• This mega PR first two commits are [3.x] CPUParticles2D - fix interpolated transforms and culling #80887 and [3.x] CPUParticles - fix non-interpolated NOTIFICATION_TRANSFORM #80827 . These should be reviewed / merged first then this PR can be rebased.
• The third commit simply disables the define for the legacy particle mode. Now that culling code is working for true global space particles, this means we can now effectively mix and match interpolated 2d items with un-interpolated particles. This can possibly be a separate small PR.
• While the third commit allows non-interpolated particles, they end up tracking AHEAD of their parent object if the parent is interpolated.
• To correct for this, the fourth and final commit performs local interpolation of the global_transform, in order to decide where to emit particles between physics ticks. This includes the machinery for reset_physics_interpolation().

[Calinou]

Tested locally in https://github.com/Calinou/platshoot/tree/physics-interpolation-test, it works as expected (as long as interpolation is disabled on the CPUParticles2D, which is the case by default). The player's jetpack particles are now smoothed out with no jittering when the player moves 🙂

[akien-mga]

Thanks!