Support taffy 0.8

[PPakalns]

Taffy 0.8 now uses tagged ptr:

The representation of many "size" types is now a tagged pointer than an enum. This is to enable calc().
The effected types are LengthPercentage, LengthPercentageAuto, Dimension, MinTrackSizingFunction, and
MaxTrackSizingFunction types.

Due to this size value retrieval is very complex and taffy values cannot be sent over threads:

• Taffy 0.8 - taffy values cannot be sent between threads due to *const () DioxusLabs/taffy#823
• Taffy 0.8 - Allow retrieving underlying size from tagged pointer. DioxusLabs/taffy#824

[Cupnfish]

Any progress?

[PPakalns]

Any progress?
@Cupnfish

Currently have other priorities. Taffy 0.7 works well enough.

Taffy 0.8 made breaking changes that make it unusable. I think even for other projects, so waiting for them to be fixed on the side of taffy or later will try to fix myself.

[PPakalns]

Example migration to newer taffy version with some workarounds in bevy:
bevyengine/bevy#21672