Do not use mutable defaults in FieldAttribute, instead allow supplying a callable for defaults of mutable types. Fixes #46824 (#46833)

test/integration/targets/include_import/public_exposure/no_bleeding.yml

@@ -0,0 +1,25 @@
+---
+- hosts: testhost
+  gather_facts: false
+  tasks:
+    - name: Static imports should expose vars at parse time, not at execution time
+      assert:
+        that:
+          - static_defaults_var == 'static_defaults'
+          - static_vars_var == 'static_vars'
+    - import_role:
+        name: static
+    - assert:
+        that:
+          - static_tasks_var == 'static_tasks'
+          - static_defaults_var == 'static_defaults'
+          - static_vars_var == 'static_vars'
+
+- hosts: testhost
+  gather_facts: false
+  tasks:
+    - name: Ensure vars from import_roles do not bleed between plays
+      assert:
+        that:
+          - static_defaults_var is undefined
+          - static_vars_var is undefined

test/integration/targets/include_import/runme.sh

@@ -81,3 +81,4 @@ ANSIBLE_STRATEGY='free' ansible-playbook tasks/test_include_dupe_loop.yml -i ../
 test "$(grep -c '"item=foo"' test_include_dupe_loop.out)" = 3
 
 ansible-playbook public_exposure/playbook.yml -i ../../inventory "$@"
+ansible-playbook public_exposure/no_bleeding.yml -i ../../inventory "$@"