fix(rhino): colors and materials are preserved on empty layers

[clairekuang]

Description

Before, we were only sending colros and materials on layers that directly had objects. Layers that didn't have any direct objects but contained other layers with objects did not have their colors and materials sent.

This fixes colors and materials on empty layers.

User Value

Better multiplayer interop workflow from rhino <-> rhino
Sample model: https://latest.speckle.systems/projects/2295cb26a0/models/63ea5caf19

Changes:

• Rhino send: color unpacker, material unpacker, and layer unpacker

Screenshots:

Original file:

Before:

After:

Validation of changes:

tested sending and receiving with the colors and materials test file

Checklist:

• [x ] My commits are related to the pull request and do not amend unrelated code or documentation.
• I have added appropriate tests.
• I have updated or added relevant documentation.

[linear]

CNX-1132 Layer colors issue

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 18.79%. Comparing base (593f95d) to head (408cb74).
Report is 1 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #542   +/-   ##
=======================================
  Coverage   18.79%   18.79%           
=======================================
  Files         240      240           
  Lines        4883     4883           
  Branches      579      579           
=======================================
  Hits          918      918           
  Misses       3934     3934           
  Partials       31       31           

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