feature #32122 [HttpFoundation] deprecate HeaderBag::get() returning an array and add all($key) instead (Simperfit)

This PR was merged into the 4.4 branch.

Discussion
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[HttpFoundation] deprecate HeaderBag::get() returning an array and add all($key) instead

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | no
| New feature?  | yes <!-- please update src/**/CHANGELOG.md files -->
| BC breaks?    | no     <!-- see https://symfony.com/bc -->
| Deprecations? | maybe <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->
| Fixed tickets | #31317  <!-- #-prefixed issue number(s), if any -->
| License       | MIT
| Doc PR        | todo <!-- required for new features -->

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 - Bug fixes must be submitted against the lowest maintained branch where they apply
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the $first param has been deprecated in the get methid
and we are adding a $key parameter to all to get all values from a key as arrays
Do we deprecated the get method ? if so this will be a little bigger in terms of changes.

Commits
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2c5a8f1bdf [HttpFoundation] deprecate using $first in get and added key in all

Author: nicolas-grekas

Tests/EventListener/AddLinkHeaderListenerTest.php

@@ -47,7 +47,7 @@ public function testOnKernelResponse()
             '</foo>; rel="preload"',
         ];
 
-        $this->assertEquals($expected, $response->headers->get('Link', null, false));
+        $this->assertEquals($expected, $response->headers->all()['link']);
     }
 
     public function testSubscribedEvents()

composer.json

@@ -24,7 +24,7 @@
         "symfony/http-kernel": ""
     },
     "require-dev": {
-        "symfony/http-foundation": "^3.4|^4.0|^5.0",
+        "symfony/http-foundation": "^4.4|^5.0",
         "symfony/http-kernel": "^4.3|^5.0"
     },
     "conflict": {