[Form] Removed usage of the ChoiceList::getIndicesFor*() methods where they don't offer any performance benefit
[Form] Fixed ChoiceList::get*By*() methods to preserve order and array keys
[Form] Fixed expanded choice field to be marked invalid when unknown choices are submitted
[Form] Improved test coverage of ChoiceList classes
[Form] Fixed regression in BooleanToStringTransformer from ed83752
Merge branch '2.2' into 2.3

* 2.2:
  [HttpKernel] added a check for private event listeners/subscribers
  [FrameworkBundle] fixed registration of the register listener pass
  [Form] Fixed regression causing invalid "WHERE id IN ()" statements
  [DependencyInjection] fixed a non-detected circular reference in PhpDumper (closes #8425)
  [Form] Fixed regression in BooleanToStringTransformer from ed83752
  [FrameworkBundle] removed obsolete code
  [Process] Close unix pipes before calling `proc_close` to avoid a deadlock

Conflicts:
	src/Symfony/Bundle/FrameworkBundle/FrameworkBundle.php
	src/Symfony/Component/HttpKernel/DependencyInjection/RegisterListenersPass.php
	src/Symfony/Component/Process/Process.php