Add cli bind test

[BryceGattis]

The CLI is largely untested right now, so I'm adding a few new tests for rez-bind.

Will likely add more tests moving forward but we can merge this one at any point.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.61%. Comparing base (9610630) to head (c5a405f).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1710      +/-   ##
==========================================
+ Coverage   58.27%   58.61%   +0.34%     
==========================================
  Files         126      126              
  Lines       17157    17157              
  Branches     3504     3504              
==========================================
+ Hits         9998    10057      +59     
+ Misses       6494     6427      -67     
- Partials      665      673       +8     

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