Move gravity direction system to Anthology

Gravity API, mixins, projectile compat, inverted effect, gravity sync and
/gravity now live in the Anthology library. Antarchy registers the Underside
region, antiwater, stale-inversion cleanup and portal gun camera roll through
GravityHooks, and depends on the local Anthology jar in anthology_jars/.

gradle.properties

@@ -50,6 +50,7 @@ structurevoidtoggle_fabric=4.4.1+1.21
 
 geckolib_version=4.8.4
 architectury_api_version=13.0.11
+anthology_version=1.0.0
 jei_version=19.27.0.336