[Form] Add a form error if post_max_size has been reached.
[Form] Moved POST_MAX_SIZE validation from FormValidator to request handler
[Form] Fixed ValidatorTypeGuesser to guess properties without constraints not to be required
bug #12004 [Form] Fixed ValidatorTypeGuesser to guess properties without constraints not to be required (webmozart)

This PR was merged into the 2.3 branch.

Discussion
----------

[Form] Fixed ValidatorTypeGuesser to guess properties without constraints not to be required

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #6645
| License       | MIT
| Doc PR        | -

Consider the following entity:

```php
class Author
{
    /**
     * @Assert\NotBlank
     */
    private $name;

    private $age;
}
```

Right now, the "required" HTML attribute is set for both fields (since the default value of the "required" option is true). IMO this is wrong.

With this fix, the ValidatorTypeGuesser guesses `false` for the "required" option unless a NotNull/NotBlank constraint is present.

Commits
-------

fd77b09 [Form] Fixed ValidatorTypeGuesser to guess properties without constraints not to be required
Merge branch '2.3' into 2.4

* 2.3:
  remove obsolete test file
  [FrameworkBundle] output failed matched path for clarification
  bug #10242 Missing checkPreAuth from RememberMeAuthenticationProvider
  [Validator] Fixed StaticMethodLoaderTest to actually test something
  [Form] Fixed ValidatorTypeGuesser to guess properties without constraints not to be required
  Use request format from request in twig ExceptionController
  [Form] Moved POST_MAX_SIZE validation from FormValidator to request handler
  [Form] Add a form error if post_max_size has been reached.
  Response::isNotModified returns true when If-Modified-Since is later than Last-Modified
  [WebProfilerBundle] turbolinks compatibility

Conflicts:
	src/Symfony/Component/Form/CHANGELOG.md
	src/Symfony/Component/HttpFoundation/Tests/ResponseTest.php
	src/Symfony/Component/Security/Core/Tests/Authentication/Provider/RememberMeAuthenticationProviderTest.php