Add baseline for deprecation testing

Problem/Motivation

symfony/phpunit-bridge 5.2.0 will bring the capability to add baseline files for deprecations, https://github.com/symfony/symfony/pull/37733

We should implement that to make simpler to avoid introducing new usages of deprecated things while legacy codebase is being cleaned up.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet