Rename has_authority condition into server_or_singleplayer

[Shatur]

I planning to do a follow-up to refine the quick start guide after it.

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 89.70%. Comparing base (c740527) to head (9408e7f).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
src/core/common_conditions.rs	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #328      +/-   ##
==========================================
- Coverage   89.77%   89.70%   -0.07%     
==========================================
  Files          37       37              
  Lines        2318     2322       +4     
==========================================
+ Hits         2081     2083       +2     
- Misses        237      239       +2     

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