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/validators.py

@@ -1,10 +1,24 @@
 import re
 
 from django.core.exceptions import ValidationError
-from django.core.validators import _lazy_re_compile, BaseValidator, URLValidator
+from django.core.validators import BaseValidator, RegexValidator, URLValidator, _lazy_re_compile
 
 from netbox.config import get_config
 
+__all__ = (
+    'ColorValidator',
+    'EnhancedURLValidator',
+    'ExclusionValidator',
+    'validate_regex',
+)
+
+
+ColorValidator = RegexValidator(
+    regex='^[0-9a-f]{6}$',
+    message='Enter a valid hexadecimal RGB color code.',
+    code='invalid'
+)
+
 
 class EnhancedURLValidator(URLValidator):
     """