Added deprecation warning on the base controller getRequest method.
minor #12656 [Controller] [FrameworkBundle] [DEPRECATION] Added a deprecation error trigger for getRequest method of the base controller (Balazs Csaba)

This PR was merged into the 2.7 branch.

Discussion
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[Controller] [FrameworkBundle] [DEPRECATION] Added a deprecation error trigger for getRequest method of the base controller

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | #12614
| License       | MIT
| Doc PR        | -

Commits
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64a9701 Added deprecation warning on the base controller getRequest method.