[Form][Validator] All index items after children are to be considered grand-children when resolving ViolationPath (fixes #11458)
[Form] FormBuilder::getIterator() now deals with resolved children
bug #11459 [Form][Validator] All index items after children are to be considered grand-children when resolving ViolationPath (Andrew Moore)

This PR was merged into the 2.3 branch.

Discussion
----------

[Form][Validator] All index items after children are to be considered grand-children when resolving ViolationPath

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | unsure, see note below
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #11458
| License       | MIT
| Doc PR        | -

#### Possible BC Break
The old behavior had unit test cases specifically testing the case of a grand-children form. However, this behavior is not documented anywhere and the fix seems to have no adverse effects on form validation. `Symfony\Component\Form\FormInterface` implements `ArrayAccess`, therefore, semantically speaking, `children[direct_child].children[grand_children]` and `children[direct_child][grand_children]` are equivalent. `offsetGet` is expected to fetch an element from `children`. I do not see why both were not considered equivalent when resolving the ViolationPath.

This commit will indeed change how some errors are mapped. However since the old mapping is (in my opinion) a bug...

Commits
-------

c64a75f [Form][Validator] All index items after children are to be considered grand-children when resolving ViolationPath (fixes #11458)
[Form] Fix PHPDoc for builder setData methods The underlying data variable is typed as mixed whereas the methods paramers where typed as array.
Merge branch '2.3' into 2.4

* 2.3: (35 commits)
  [Form] Fix PHPDoc for builder setData methods The underlying data variable is typed as mixed whereas the methods paramers where typed as array.
  fixed CS
  [Intl] Improved bundle reader implementations
  [Console] guarded against invalid aliases
  switch before_script to before_install and script to install
  fixed typo
  [HttpFoundation] Request - URI - comment improvements
  [Security] Added more tests
  remove `service` parameter type from XSD
  [Intl] Added exception handler to command line scripts
  [Intl] Fixed a few bugs in TextBundleWriter
  [Intl] Updated icu.ini up to ICU 53
  [Intl] Removed non-working $fallback argument from ArrayAccessibleResourceBundle
  Use separated function to resolve command and related arguments
  [SwiftmailerBridge] Bump allowed versions of swiftmailer
  [FrameworkBundle] Remove invalid markup
  [Intl] Added "internal" tag to all classes under Symfony\Component\Intl\ResourceBundle
  Remove routes for removed WebProfiler actions
  [Security] Fix usage of unexistent method in DoctrineAclCache.
  backport more error information from 2.6 to 2.3
  ...

Conflicts:
	.travis.yml
	src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
	src/Symfony/Component/DependencyInjection/Tests/Loader/XmlFileLoaderTest.php
	src/Symfony/Component/HttpKernel/Kernel.php
	src/Symfony/Component/Process/PhpExecutableFinder.php