Replace RECOG.TestGroup by new CheckSize helper

[fingolfin]

It is not the job of this package to test recog, but the function RECOG.TestGroup is written for that task, and e.g. performs group recognition multiple times. But we really only want to use recog to compute a group size in order to test our code. So let's do just that, and nothing more.

Description of your PR

Checklist for the reviewer

General

• [ ] All functions have unit tests

Functions constructing generators of maximal subgroups

• [ ] The code which computes and then stores the sizes is correct. To do this one confers to the tables referenced by the code. Tests for the group size should use RECOG.TestGroup from the recog package.
• [ ] The test suite checks whether all constructed generators are sensible. That is it tests the generators'
  • [ ] determinants (and if applicable also the spinor norms are correct), and
  • [ ] compatibility with the correct form,
  • [ ] DefaultFieldOfMatrixGroup returns the correct field.

Functions assembling the list of all maximal subgroups of a certain group

• [ ] The code agrees with the tables in section 8.2 of the book "The Maximal Subgroups of the Low-dimensional Finite Classical Groups".

The reviewer doesn't need to compare our results to magma's results. That's the job of the person implementing the code.

[codecov[bot]]

Codecov Report

Merging #98 (4f17f6b) into main (b1944c3) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #98   +/-   ##
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  Coverage   95.66%   95.66%           
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  Files          14       14           
  Lines        2860     2860           
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  Hits         2736     2736           
  Misses        124      124