IBX-12840: Bumped ibexa/code-style to 2.3.1

[ViniTou]

🎫 Issue	IBX-12840

Description:

Bumped ibexa/code-style from ^1.1 to ~2.3.1 and applied the resulting php-cs-fixer changes.

• The reformatting is in its own commit, separate from the composer bump
• Added ibexa/doctrine-migrations ~4.6.x-dev to require-dev: ibexa/core now requires the untagged ibexa/doctrine-migrations dev branch, which only a root package can allow under minimum-stability: stable

For QA:

No QA required.

Documentation:

No documentation required.