COHIV-133: Don't overwrite self.field.name in BooleanFieldDefaultTrueListFilter

[MarcoSteinacher]

• Avoids overwriting self.field.name, which caused the bug.
• Simplifies code and builds on existing lookup_kwarg and lookup_var variables of parent class.
• Adds the model name to the filter label, if the filter uses a boolean field of a related object (to distinguish filters for multiple active fields).
• Adds test.

---

I confirm that I have read the Contributor Agreement v1.1, agree to be bound on them and confirm that my contribution is compliant.

[github-actions]

Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
django/geno
admin.py
models.py
django/geno/tests
test_admin.py					241
django/reservation/tests
test_models.py
Project Total

This report was generated by python-coverage-comment-action