Fix T73304: Crash using force fields and hair dynamics

This implements a better heuristic for identifying if cloth or hair is
being dealt with (checking hairdata, instead of primitive_num).

The issue was caused by a change in primitive counting in rBd42a7bbd6ea5

I'm also adding some safeguards to avoid ever computing pressure for
hair. This shouldn't really be necessary, but it's good to be sure.

Integrate hair collisions with cloth collision

This integrates hair collisions with the new cloth collision system,
greatly improving reliability, and reducing the amount of hair-specific
code paths in the cloth code.

The removes all the point constraint based collision stuff, instead
implementing segment impulse based collisions, using the same collision
response code as the normal cloth solver.

The hair system can now also collide with the emitter if it is a
collision object.

Reviewed By: mano-wii, Sebastian Parborg

Differential Revision: https://developer.blender.org/D6545

Merge branch 'blender-v2.82-release'

Fix T71620: broken particle collisions due to rB0666ece2e2f9

An optimisation in the collision system for cloth (static collisions),
broke the particle collisions, as they take motion into account. This
restores the moving BVH required for the particle collisions, while
keeping the optimisation for the cloth collisions.

Reviewed By: mano-wii

Maniphest Tasks: T71620

Differential Revision: https://developer.blender.org/D6560

OpenVDB: Disable simplification when rendering sparse

Simplification would mess up some values that Cycles needs when doing
sparse renders, so this commit disables render simplification when
sparse rendering is enabled, ensuring the values will be correct.

OpenVDB: Expose `index_offset` property in RNA

OpenVDB: Set `clipping` to 0.0

OpenVDB: Make filepath of current frame available

This makes `abs_path` in the OpenVDB modifier return the path to the
frame that should currently be read (taking into account the current
frame, the frame offset, and frame overrides).

This is a bit hackish, as it duplicates the frame calculation and path
generation code, but it was the quickest and easiest way to achieve
this, in contrast to adapting and exposing the existing functions to
work with this use-case.

OpenVDB: Add sparse render option

This option prevents the cache from being loaded into memory.

OpenVDB: Make "simplify" available for render