Closes #12246: General cleanup of utilities modules

* Clean up base modules

* Clean up forms modules

* Clean up templatetags modules

* Replace custom simplify_decimal filter with floatformat

* Misc cleanup

* Merge ReturnURLForm into ConfirmationForm

* Clean up import statements for utilities.forms

* Fix field class references in docs

netbox/utilities/forms/fields/csv.py

@@ -1,14 +1,9 @@
-import csv
-from io import StringIO
-
 from django import forms
 from django.contrib.contenttypes.models import ContentType
 from django.core.exceptions import MultipleObjectsReturned, ObjectDoesNotExist
 from django.db.models import Q
-from django.utils.translation import gettext as _
 
 from utilities.choices import unpack_grouped_choices
-from utilities.forms.utils import parse_csv, validate_csv
 from utilities.utils import content_type_identifier
 
 __all__ = (