Move scaler.py to core

[MarionBWeinzierl]

Description

Instead of taking just the daily means functions out of scaler, this PR moves the whole class to core, to make it functionality available elsewhere in the code.

Fixes #406

Type of change

• New feature (non-breaking change which adds functionality)
• Optimization (back-end change that speeds up the code)
• Bug fix (non-breaking change which fixes an issue)

Key checklist

• Make sure you've run the pre-commit checks: $ pre-commit run -a
• All tests pass: $ poetry run pytest

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.48%. Comparing base (56ccf57) to head (f4a0c91).
Report is 47 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #407      +/-   ##
===========================================
+ Coverage    96.27%   96.48%   +0.20%     
===========================================
  Files           34       35       +1     
  Lines         2659     2730      +71     
===========================================
+ Hits          2560     2634      +74     
+ Misses          99       96       -3     

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[davidorme]

Hmmm. Not sure how I feel about this.

That's partly because this is going to change with the move to an AcclimationModel API (see #394), but also I think the correct way to do this is probably to separate out the core of the wrapping and subsetting engine in here from the SubdailyPModel specific components. That's more of a job, but I guess I think that rather than moving the very SubdailyPModel specific implementation into core now it would be better to import it from its current location for the meantime. Then the usage can help guide the breaking out the underlying shared functionality into core?