Depreciate injection of Request instances

[chalasr]

Q	A
Branch?	master
BC breaks?	yes (small)
Deprecations?	yes
Tests pass?	yes

This depreciates the injection of Request instances in order to totally avoid this practice in 2.0. That concerns most of our Event classes.

Warning triggered by Scrutinizer:

Bug
You have injected the Request via parameter $request. This is generally not recommended as there might be multiple instances during a request cycle (f.e. when using sub-requests). Instead, it is recommended to inject the RequestStack and retrieve the current request each time you need it via getCurrentRequest().

The proposed deprecation way consists into:

• adding a default value (null) for constructors/setters arguments type hinted as Request (BC break)
• document the corresponding properties+members as deprecated
• trigger a E_USER_DEPRECATED notice when the deprecated methods are called with a Request as argument.

The recommended alternative is to inject the RequestStack instead.
For Event classes, the user will be responsible of injecting the request stack into their event listeners to be able to use it.

All changed classes are instantiated internally, I think this should not be an hard BC breaking for most people.
Any thoughts?

---

• Pre-remove the practice from our code (when RequestStack exists)
• Documentation needs to be updated with an example of @request_stack injection&usage

[chalasr]

Pending markitosgv/JWTRefreshTokenBundle#45