Fix mysql_user on_new_username IndexError (#642)

* fix tuple indexerror when no accounts are found

* Fix tests for update_password not executed

* Add test for case where existing user have different password

* lint to prevent warning about jinja templating in when clause

* Refactor get_existing_authentication to return a list of all row found

Previously we were returning only the first row found. We need to be
able to see if there is a difference in the existing passwords.

* Refactor host option to be optional

This make it possible to use the same method from mysql_user to help
update_password retrieve existing password for all account with the same
username independently of their hostname. And from mysql_info to get
the password of a specif user using WHERE user = '' AND host = ''

* Add change log fragment

* Add link to the PR in the change log

* lint for ansible devel

* Fix templating type error could not cconvert to bool with ansible devel

* Revert changes made for ansible-devel that broke tests for Ansible 2.15

* Revert changes made for ansible-devel that broke tests

* Cut unnecessary set, uniqueness is ensured by the group_by in the query

* Cut auth plugin from returned values when multiple existing auths exists

Discussed here:
https://github.com/ansible-collections/community.mysql/pull/642/files#r1649720519

* fix convertion of list(dict) to list(tuple)

* Fix test for empty password on MySQL 8+

tests/integration/targets/test_mysql_variables/tasks/mysql_variables.yml

@@ -47,8 +47,8 @@
     # Verify mysql_variable successfully updates a variable (issue:4568)
     #
     - set_fact:
-         set_name: 'delay_key_write'
-         set_value: 'ON'
+        set_name: 'delay_key_write'
+        set_value: 'ON'
 
     - name: set mysql variable
       mysql_variables:
@@ -74,8 +74,8 @@
     # Verify mysql_variable successfully updates a variable using single quotes
     #
     - set_fact:
-         set_name: 'wait_timeout'
-         set_value: '300'
+        set_name: 'wait_timeout'
+        set_value: '300'
 
     - name: set mysql variable to a temp value
       mysql_variables:
@@ -105,8 +105,8 @@
     # Verify mysql_variable successfully updates a variable using double quotes
     #
     - set_fact:
-         set_name: "wait_timeout"
-         set_value: "400"
+        set_name: "wait_timeout"
+        set_value: "400"
 
     - name: set mysql variable to a temp value
       mysql_variables:
@@ -132,8 +132,8 @@
     # Verify mysql_variable successfully updates a variable using no quotes
     #
     - set_fact:
-         set_name: wait_timeout
-         set_value: 500
+        set_name: wait_timeout
+        set_value: 500
 
     - name: set mysql variable to a temp value
       mysql_variables:
@@ -251,8 +251,8 @@
     # Verify mysql_variable works with the login_user and login_password parameters
     #
     - set_fact:
-         set_name: wait_timeout
-         set_value: 77
+        set_name: wait_timeout
+        set_value: 77
 
     - name: query mysql_variable using login_user and password_password
       mysql_variables:
@@ -291,8 +291,8 @@
     # Verify mysql_variable fails with an incorrect login_password parameter
     #
     - set_fact:
-         set_name: connect_timeout
-         set_value: 10
+        set_name: connect_timeout
+        set_value: 10
 
     - name: query mysql_variable using incorrect login_password
       mysql_variables: