refactor(rhino): CNX-19 adds render materials to objects and layers

[clairekuang]

Refactors render materials to be sent as a List<RenderMaterialProxy> on the root commit, which contains the object ids of objects using the render material. Also adds render materials to layers.

sample commit: https://app.speckle.systems/projects/93200a735d/models/cbacd3eaeb

Notes:

1. might want to refactor send and recieve so that layers are processed separately from objects. Currently, creating layers in the object iteration means higher complexity in assigning / creating render materials as well. RhinoHostObjectBuilder on receive is looking especially ugly.
2. the built in pbr materials in rhino, eg Gem, are not translated well into our RenderMaterial class, especially with a transparency set to 1.

[linear]

CNX-19 Rhino: Base implementation

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 8.00%. Comparing base (c2a53f6) to head (7b199c2).

Additional details and impacted files

@@          Coverage Diff          @@
##             dev     #74   +/-   ##
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  Coverage   8.00%   8.00%           
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  Files        228     228           
  Lines       4371    4371           
  Branches     489     489           
=====================================
  Hits         350     350           
  Misses      4011    4011           
  Partials      10      10           

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