cs fix

object type

conversionFailedUnserialization

type hinting & finally restore error handler

cs: use function

type hint

sort use alphabetically

code quality improvements

1. Use the actual dsdriver distribution
2. Introduced `AbstractPlatform::getCharMaxLength()` since `CHAR` and `VARCHAR` limitations are different on DB2.

And then we don't need to wait till v3 to not require comments on the
JsonType.

It is a somewhat fragile thing to do.

I think distinguish was the intended meaning here, not dismantle.

Fix PSR2 rules : "As per PSR2, the static declaration should come after the visibility declaration."

#2794 allowing `DateTimeImmutable` instances when converting in mutable date types - reverts unintentional BC break

Closes #1882

see https://github.com/doctrine/doctrine2/pull/1104#issuecomment-51755834