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/constants.py

@@ -31,21 +31,6 @@ FILTER_TREENODE_NEGATION_LOOKUP_MAP = dict(
     n='in'
 )
 
-
-# Keys for PostgreSQL advisory locks. These are arbitrary bigints used by
-# the advisory_lock contextmanager. When a lock is acquired,
-# one of these keys will be used to identify said lock.
-#
-# When adding a new key, pick something arbitrary and unique so
-# that it is easily searchable in query logs.
-
-ADVISORY_LOCK_KEYS = {
-    'available-prefixes': 100100,
-    'available-ips': 100200,
-    'available-vlans': 100300,
-    'available-asns': 100400,
-}
-
 #
 # HTTP Request META safe copy
 #