More boundschecks for scaling by (inverse) mass matrices

[ranocha]

CC @JoshuaLampert

Closes #310

[JoshuaLampert]

Thanks! I have two suggestions/questions.

[codecov]

Codecov Report

Attention: Patch coverage is 93.47826% with 3 lines in your changes missing coverage. Please review.

Project coverage is 91.85%. Comparing base (00164c7) to head (2d229a2).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/filter.jl	33.33%	2 Missing ⚠️
src/general_operators.jl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #311      +/-   ##
==========================================
+ Coverage   91.83%   91.85%   +0.02%     
==========================================
  Files          35       35              
  Lines        5571     5587      +16     
==========================================
+ Hits         5116     5132      +16     
  Misses        455      455              

Flag	Coverage Δ
unittests	91.85% <93.47%> (+0.02%)	⬆️

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[coveralls]

coverage: 92.58% (+0.02%) from 92.56%
when pulling 2d229a2 on hr/scale_tests
into 00164c7 on main.