Update the project to Symfony 6.3

[javiereguiluz]

This PR will be WIP until 6.3 is released as stable.

[javiereguiluz]

I've updated to Symfony 6.3 beta 2 and I still see this direct deprecation:

The problem is that a Symfony internal Logger class extends a Monolog class marked as final:

I have two questions:

• Why is it marked as "direct deprecation" instead of "indirect deprecation"?
• Are we aware of this in the Symfony code repository so we can fix it before the final release?

[wouterj]

Direct vs indirect may be a bug (the logic around this is a bit fragile).

The deprecation itself is known and unrelated to a Symfony upgrade, but rather a Monolog update: symfony/symfony#47096 There is no need to fix this before the final release

[stof]

Direct vs indirect deprecation is fragile for deprecations triggered by the DebugClassLoader right now