fix: removed Nav Container plugin and fixed Navigation Link plugin

[fsbraun]

Description

This PR

• Removes the Nav Container plugin. Its functionality has already been taken over by the "Container" option of the Navigation plugin. The template code has been moved to the Navigation plugin effectively re-enabling the responsiveness of Bootstrap 5 navbar: On small viewports the navbar automatically collapses.
• The navigation link does now render icons
• Improved support for RTL setups

Related issues

• 189

• 190

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 66.66667% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 86.78%. Comparing base (f11feee) to head (37fac26). Report is 6 commits behind head on master.

Files	Patch %	Lines
...ontend/contrib/navigation/frameworks/bootstrap5.py	0.00%	1 Missing and 1 partial :warning:
djangocms_frontend/contrib/navigation/models.py	50.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #192 +/- ## ========================================== - Coverage 86.93% 86.78% -0.16% ========================================== Files 120 120 Lines 3107 3109 +2 Branches 330 331 +1 ========================================== - Hits 2701 2698 -3 - Misses 304 307 +3 - Partials 102 104 +2 ```

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