cad/opencascade: upgrade to 7.7.0-beta

[thierry]

Summary

See https://dev.opencascade.org/content/occt-770-beta-version-available.

Also add draco as a dependency.

Note: I do not intend to commit this beta version, this is just to check how the consumers will behave!

Test Plan

ATM the following ports depend on OCCT:

cad/freecad
cad/gmsh
cad/horizon-eda
cad/kicad
cad/kicad-devel
cad/py-ocp
graphics/f3d
math/py-topologic
math/topologic
science/elmerfem

Please check that everything would be OK with 7.7.0.

[thierry]

Since everything seems clear, I have just upgraded OpenCascade to 7.7.0 final.