Fix dependent fields in a formset

[mardukbp]

This PR provides a general solution for #136 based on the solution by @rez0n.

The contributions of this solution are the following:

• Find the closest common ancestor of two chained selects instead of assuming it is a form.
• Try to find the dependent field by its name attribute using a two-fold search strategy: exact match otherwise ends with

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.19%. Comparing base (f61b09c) to head (a59d972).
Report is 30 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #316      +/-   ##
==========================================
- Coverage   98.21%   98.19%   -0.02%     
==========================================
  Files           7        7              
  Lines         280      277       -3     
==========================================
- Hits          275      272       -3     
  Misses          5        5              

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[codingjoe]

Don't hesitate to use template literals. You may use everything included in Baseline 2024 ;)

[mardukbp]

I know string literals, but feared breaking django-select2 for someone with an old browser. But if you say it's fine :)