minor fixes on sfFormField and sfSessionStorage

[pedromellofh]

sfFormField lacks defaults in __construct and sfSessionRestore throws a warning when calls session_regenerate_id uppon an already started

[alquerci]

ℹ️ Ref of symfony implémentation of native regenerate

https://github.com/symfony/symfony/blob/v7.2.5/src/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php#L187

[thePanz]

Thanks @alquerci for the pointer to SF 7.2 implementation.

@pedromellofh I would follow that example here, and NOT silence the call triggering the warning.

Would you adapt the code, by taking in the example from SF 7.2 linked by @alquerci ? thank you