Add Device model commands manager tests

[kbeaugrand]

Description

What's new?

• Add unit tests on device model commands manager

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Tests
• Other

[codecov]

Codecov Report

Merging #216 (f34a1b1) into main (c3201b7) will increase coverage by 1.60%.
The diff coverage is n/a.

@@           Coverage Diff            @@
##            main    #216      +/-   ##
========================================
+ Coverage   6.77%   8.38%   +1.60%     
========================================
  Files         71      71              
  Lines       2361    2361              
========================================
+ Hits         160     198      +38     
+ Misses      2201    2163      -38     

Impacted Files	Coverage Δ
...rtal/Server/Managers/DeviceModelCommandsManager.cs	90.47% <0.00%> (+90.47%)	⬆️

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