feat: Add rector rule to automatically migrate to the new createInstanceWithMocks

[come-nc]

Description

Migrate test classes to the new method createInstanceWithMocks.

Motivation and context

See nextcloud/server#64736

How has this been tested?

Unit test included, was also used on server code base with success.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

PR checklist

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING.md document.
• I have added tests to cover my changes.

[nickvergessen]

Is that related to the warning PHPUnit 12 is giving? Or are we migrating to something that then even more disallows us to move forward?
TLDR of the warning is "anything that is a mock and not used should be a stub" or something a like

OCA\Notifications\Tests\Unit\WebPushClientTest::testConstructRegeneratesVapidKeysWhenDecryptionFails
No expectations were configured for the mock object for OCP\Http\Client\IClientService. Consider refactoring your test code to use a test stub instead. The #[AllowMockObjectsWithoutExpectations] attribute can be used to opt out of this check.

/home/nickv/Nextcloud/36/server/appsbabies/notifications/tests/Unit/WebPushClientTest.php:49