Remove bs3 styles from crispy_forms_field

[smithdc1]

Here is another step towards decoupling crispy-forms-core from template packs.

This removes the bs3 styles which are currently being added in crispy_forms_field.py.

Interestingly, and at least from what I can see in the docs, form-control-danger is not the right way of adding errors in bs3. 'has-error' is the solution and that's already built into the templates. This made it much easier to put the remaining logic into the templates. I suspect the bs4 templates will not be quite so easy.

Here are before/after images (no change hopefully) 🤞

Before:

After:

[codecov-io]

Codecov Report

Merging #1003 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1003      +/-   ##
==========================================
- Coverage   97.06%   97.06%   -0.01%     
==========================================
  Files          24       24              
  Lines        2728     2724       -4     
  Branches      241      239       -2     
==========================================
- Hits         2648     2644       -4     
  Misses         39       39              
  Partials       41       41

Impacted Files	Coverage Δ
crispy_forms/templatetags/crispy_forms_field.py	92.23% <ø> (-0.3%)	⬇️

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[smithdc1]

@carltongibson Appreciate your thoughts on this. It's another step towards being able to split out the template packs.

[codecov-commenter]

Codecov Report

Merging #1003 (364471a) into main (93a873b) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1003      +/-   ##
==========================================
- Coverage   97.27%   97.26%   -0.01%     
==========================================
  Files          23       23              
  Lines        2931     2927       -4     
  Branches      243      241       -2     
==========================================
- Hits         2851     2847       -4     
  Misses         39       39              
  Partials       41       41              

Flag	Coverage Δ
unittests	97.26% <ø> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
crispy_forms/templatetags/crispy_forms_field.py	94.17% <ø> (-0.22%)	⬇️

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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