WIP: enforce a single scaled on a CollectionSet

[ctb]

Addresses #3386

#3387 changed select to update Record.scaled to the desired scaled value. This PR changes CollectionSet to require that all scaled values be the same, which can now be achieved by running select ;).

It also adds a new method Collection::min_max_scaled() which makes it easy to retrieve scaled for a Collection.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 86.46%. Comparing base (97e7808) to head (2ce356d).

Files with missing lines	Patch %	Lines
src/core/src/collection.rs	50.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           latest    #3397      +/-   ##
==========================================
- Coverage   86.47%   86.46%   -0.01%     
==========================================
  Files         137      137              
  Lines       16095    16100       +5     
  Branches     2219     2219              
==========================================
+ Hits        13918    13921       +3     
- Misses       1870     1872       +2     
  Partials      307      307              

Flag	Coverage Δ
hypothesis-py	25.43% <ø> (ø)
python	92.40% <ø> (ø)
rust	62.29% <50.00%> (-0.01%)	⬇️

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