Fix empty process argument escaping on Windows
[Process] Fix CS
[Process] Add failing test for #8739
[Process] Fix #8739
[Process] Avoid zombie process in case of unit tests failure
[Process] Add more precision to Process::stop timeout
Merge branch '2.2' into 2.3

* 2.2:
  corrected English grammar (s/does not exists/does not exist)
  [Process] Add more precision to Process::stop timeout
  [Process] Avoid zombie process in case of unit tests failure
  [Process] Fix #8739
  [Process] Add failing test for #8739
  [Process] Fix CS
  Fixed documentation grammar for AuthenticationManagerInterface::authenticate()
  [Validator] fixed the wrong isAbstract() check against the class (fixed #8589)
  [TwigBridge] Prevent code extension to display warning
  Use strstr instead of strpos

Conflicts:
	src/Symfony/Component/Finder/Shell/Command.php
	src/Symfony/Component/Process/Process.php
[Process] Fix #8742 : Signal-terminated processes are not successful
[Process] Fix #8746 : slowness added in unit tests since #8741
[Process] Revert change
Merge branch '2.2' into 2.3

* 2.2:
  [Process] Revert change
  [Process] Fix #8746 : slowness added in unit tests since #8741
merged branch romainneutron/fix-8742 (PR #8744)

This PR was merged into the 2.3 branch.

Discussion
----------

[Process] Fix #8742 : Signal-terminated processes are not successful

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | require #8741 to be merged to pass tests
| Fixed tickets | #8742
| License       | MIT

Commits
-------

909fab6 [Process] Fix #8742 : Signal-terminated processes are not successful
Merge branch '2.3'

* 2.3:
  [Process] Revert change
  [Process] Fix #8746 : slowness added in unit tests since #8741
  [Process] Fix #8742 : Signal-terminated processes are not successful
  corrected English grammar (s/does not exists/does not exist)
  [Process] Add more precision to Process::stop timeout
  [Process] Avoid zombie process in case of unit tests failure
  [Process] Fix #8739
  [Process] Add failing test for #8739
  [Process] Fix CS
  [TwigBridge] removed superflous ; when rendering form_enctype() (closes #8660)
  Fixed documentation grammar for AuthenticationManagerInterface::authenticate()
  [Validator] fixed the wrong isAbstract() check against the class (fixed #8589)
  [TwigBridge] Prevent code extension to display warning
  Fix internal sub-request creation
  [FrameworkBundle] made code more generic
  [Form] Moved auto_initialize option to the BaseType
  Use strstr instead of strpos
  Make sure ContextErrorException is loaded during compile time errors
  Fix empty process argument escaping on Windows
  Ignore null value in comparison validators

Conflicts:
	src/Symfony/Component/Debug/Tests/ErrorHandlerTest.php
	src/Symfony/Component/HttpKernel/Tests/Fragment/InlineFragmentRendererTest.php
	src/Symfony/Component/Process/Process.php