Add benchmark suite for single time series and rqatrend on testdata cube

[felixcremer]

This adds the benchmarks to a benchmark folder so that we can run it on the latest commit and on the first commit.
We should set it up so that it would be automatically run on every PR.

See #89 for the current benchmarks.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.26%. Comparing base (b63c875) to head (76809c6).
Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main      #97       +/-   ##
===========================================
+ Coverage   47.18%   61.26%   +14.07%     
===========================================
  Files           7        7               
  Lines         320      253       -67     
===========================================
+ Hits          151      155        +4     
+ Misses        169       98       -71     

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