fix(test): restore main CI after the ApiTestCase extraction

[soyuka]

main is currently red: 24 failing jobs on c587c81e0. Two distinct causes, both from PRs merged earlier today on stale CI runs — neither is merge-up damage. The merge-up simply made main complete a CI run for the first time since 150911ef7.

1. ApiTestCase FQCN fatal — takes down the whole matrix

Internal error: Class "ApiPlatform\Symfony\Bundle\Test\ApiTestCase" not found

#7887 moved the test helpers to ApiPlatform\Test and deleted src/Symfony/Bundle/Test/. 11 files still used the old FQCN — some merged on main after #7887 (#8283, #8310, #7870, #8491), some brought up from 4.3/4.4 (#8451, #8505, #8416, #8521, #8508), where the old FQCN is still correct. One fatal killed every PHPUnit job and PHPStan.

2. GraphiQL csp_nonce double — graphql x4

EntrypointActionTest::testGetHtmlAction
Prophecy\Exception\Call\UnexpectedCallException:
  Unexpected method call: getFunction("csp_nonce")
  expected calls were: render(* [, ...])

#8310 made GraphiQlAction ask Twig for csp_nonce and updated GraphiQlActionTest, but missed EntrypointActionTest, which builds the same action.

3. Deprecated BC shims (the structural part)

#7887 moved eight public classes with no deprecation path. Users extend ApiTestCase in their own suites, so they hit a bare "class not found" on upgrade. It also breaks every merge-up:

branch	old FQCN present	files using it
4.3	yes	263
4.4	yes	279
main	deleted	11 (fixed here)

Without a shim this recurs on every merge-up until 4.4 reaches EOL. The shims restore all eight at the old FQCNs, each emitting trigger_deprecation:

• ApiTestCase — abstract, subclassed
• ClientTrait, ApiTestAssertionsTrait, Constraint\ArraySubsetTrait — traits, wrapped via use
• Client, Response, Constraint\ArraySubset, Constraint\MatchesJsonSchema — final, so class_alias (they cannot be subclassed)

Verified at runtime through the real autoloader, not just php -l: all 5 classes resolve to their new counterparts and all 3 traits exist.

api-platform/test and symfony/deprecation-contracts are added to src/Symfony/composer.json, which previously declared neither.

Note on the strict deprecation job

PHPUnit (no deprecations) runs max[self]=0. Nothing fires today since main's own tests now use the new FQCN. A future merge-up that brings an old-FQCN file will trip that job rather than fataling the whole suite — a better failure mode, but it still wants the FQCN rewritten on merge-up. ignoreFile=./tests/.ignored-deprecations is available if you'd prefer to silence it.

Unrelated, spotted while here

api-platform/test is not in the CI component matrix in ci.yml (18 components listed, it isn't one). It ships — it's in the root replace and matched by the pmu glob — but is never tested in isolation. Same gap eb6bd572b had to fix for MCP. Not addressed here.