New SkCurve type with multiple curve segments

- Converted all linear force stuff into a single affector,
  used at either spawn or update time appropriately.
  The new affector can either set or adjust velocity.
- Converted lifetime to a curve.
- Removed SkRangedFloat, initial velocity params, etc.

Looks like a large addition, but that's mostly down to the
JSON getting bigger. There's a net reduction in LoC.

Bug: skia:
Change-Id: Iac7417f15f96d0313efd08c4b26dc3250b80fa77
Reviewed-on: https://skia-review.googlesource.com/c/192102
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
6 files changed