Update src/Symfony/Component/HttpFoundation/Request.php

This makes `getContentType()` work when a regular form is submitted.
[Form] Choice children can be template customized like collection
[Serializer] Added PropertyNormalizer, a new normalizer that maps an object's properties to an array
Call AuthenticationManager in AnonymousAuthenticationListener
[HttpKernel] Extract method to make callable controller in ControllerResolver

correct naming
[Form][Validator] All index items after children are to be considered grand-children when resolving ViolationPath (fixes #11458)
add allow_html5 option to date and time FormType to disable HTML5 date input when widget is set to single_text

remove unnecessary test when creating datetime format data transformer
[MonologBridge] Ignore empty context/extra by default in the ConsoleFormatter
[WebProfilerBundle] turbolinks compatibility
[Translation] made XliffFileDumper support CDATA sections.
[FrameworkBundle] Add Event Dispatcher debug command
[Form] FormBuilder::getIterator() now deals with resolved children
[Twig][Form] Moved configuration key twig.form.resources to
twig.form_themes
fix handling of empty sequence items

When a line contains only a dash it cannot safely be assumed that
it contains a nested list or an embedded mapping. If the next line
starts with a dash at the same indentation, the current line's item
is to be treated as `null`.
[DI] Added safeguards against invalid config in the YamlFileLoader

Exceptions explaining the mistake are better than fatal errors or weird
notices appearing when trying to deal with such invalid data.
Closes #11333
updated CHANGELOG for 2.3.19
update CONTRIBUTORS for 2.3.19
updated VERSION for 2.3.19
updated CHANGELOG for 2.4.9
updated VERSION for 2.4.9