[Security] Allow custom user identifier for X509 authenticator

[Spomky]

Q	A
Branch?	6.3
Bug fix?	no
New feature?	yes
Deprecations?	no
Tickets	Fix #47354
License	MIT
Doc PR	to be created

This PR allows defining a custom user identifier instead of the hardcoded emailAddress.
It also adds a new option for the firewall configuration:

# config/packages/security.yaml
security:
    # ...

    firewalls:
        main:
            # ...
            x509:
                provider: your_user_provider
                user_identifier: CN # default to emailAddress

💬 Discussion: user identifier regex changed
Note that the regex is changed. The previous one was able to find an email address as expected, but now that the common name may not contain a @ (or may contain more than one), it is required to update this part.
It does not impact the previously merged PR #33759, but I prefer highlight the fact that it can now catch invalid email addresses set in emailAddress.

[nicolas-grekas]

One minor thing and good to go on my side, thanks.

[fabpot]

Thank you @Spomky.