Add changelog fragment and CI tests

changelogs/fragments/40-mysql_user_fix_error_when_host_all_used.yml

@@ -0,0 +1,2 @@
+bugfixes:
+- mysql_user - fix module's crush when modifying a user with ``host_all`` (https://github.com/ansible-collections/community.mysql/issues/39).

tests/integration/targets/test_mysql_user/tasks/main.yml

@@ -196,6 +196,7 @@
         name: '{{ user_name_1 }}'
         priv: '%db.*:INSERT'
         append_privs: yes
+        host_all: yes
         password: '{{ user_password_1 }}'
 
     - name: show grants access for user1 on multiple database