Internal and documentation improvements

[HereAround]

• Remove auxiliary function _strict_transform (no longer needed thx to Improve performance of strict transform under toric blowups #4484).
• Allow users to access torsion_sections and add its documentation.
• I found that the documentation of more functions was not linked/visible on the website.
• Convenience method to compute a random flux with prescribed properties for an F-theory model.

I did not (yet) check in detail if all our docstrings are also quote in the docs folder/explained there. Note that those docstring that do not appear in the docs folder do not appear on the website. Maybe @emikelsons could verify if more is missing?

Modulo this (minor) caveat, the above should be ready for review.

[codecov]

Codecov Report

Attention: Patch coverage is 77.77778% with 4 lines in your changes missing coverage. Please review.

Project coverage is 84.39%. Comparing base (767415a) to head (7883d7b).
Report is 120 commits behind head on master.

Files with missing lines	Patch %	Lines
.../FTheoryTools/src/AbstractFTheoryModels/methods.jl	33.33%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4486   +/-   ##
=======================================
  Coverage   84.39%   84.39%           
=======================================
  Files         672      672           
  Lines       88690    88697    +7     
=======================================
+ Hits        74846    74855    +9     
+ Misses      13844    13842    -2     

Files with missing lines	Coverage Δ
...heoryTools/src/AbstractFTheoryModels/attributes.jl	99.60% <100.00%> (+<0.01%)	⬆️
...heoryTools/src/AbstractFTheoryModels/properties.jl	98.33% <100.00%> (+0.02%)	⬆️
...ental/FTheoryTools/src/FamilyOfG4Fluxes/methods.jl	100.00% <100.00%> (+10.00%)	⬆️
experimental/FTheoryTools/src/auxiliary.jl	80.75% <ø> (+0.91%)	⬆️
.../FTheoryTools/src/AbstractFTheoryModels/methods.jl	77.39% <33.33%> (-0.62%)	⬇️

... and 2 files with indirect coverage changes

[emikelsons]

Looks good and the tests pass