Add dynamic field to field struct

This change adds a dynamic field indicator to the field struct.  This is so
we can remove the dynamic fields from an existing schema before merging the
dynamic schema and actual schema to prevent removed dynamic fields form being
incorrectly left behind on the schema.

Issue:
https://github.com/rancher/rancher/issues/12698

types/types.go

@@ -136,6 +136,7 @@ type Field struct {
 	InvalidChars string      `json:"invalidChars,omitempty"`
 	Description  string      `json:"description,omitempty"`
 	CodeName     string      `json:"-"`
+	DynamicField bool        `json:"dynamicField,omitempty"`
 }
 
 type Action struct {