Re-combine physics + fixtures components

[metalgearsloth]

trafficstars

RT does not support component groups at all and keeping them separate is extremely annoying. The only reason they're even separate to begin with was the lack of delta states at the time and fixture compstates chugging people's bandwidth. Preferably you'd do this after an easy way to add delta state support is added without having to manually track this.

Alternatively if we get dependent components that gives caching performance (when we get struct comps right?)