[ComposerBased] Pin version-bound tests to a test-specific composer.json instead of the repo root

[TomasVotruba]

Problem

ComposerBasedTest had no provideComposerJsonFilePath() override, so InstalledPackageResolver fell back to the repo root composer.json (getcwd()) to resolve the version-bound rules. The version-bound fixtures then depended on whatever doctrine/* happened to be installed locally, and on the root's declared ranges — not on a version the test controls.

This surfaced via rectorphp/rector-src#8363: once a distributed package resolves to its lowest declared version, the root doctrine/orm: ^3.0 floor dropped the ORMSetup >=3.5 renames and version_bound_orm_setup_renames broke.

Fix

Pin the version-bound tests to a test-specific composer.json, via the existing provideComposerJsonFilePath() hook:

protected function provideComposerJsonFilePath(): ?string
{
    return __DIR__ . '/composer.json';
}

{
    "require": {
        "doctrine/orm": "^3.5",
        "doctrine/dbal": "^4.0"
    }
}

Those floors match the APIs the three fixtures target (doctrine/orm >=3.5 for the ORMSetup renames and >=2.9 for the annotation-to-attribute pass, doctrine/dbal >=4.0 for the getSchemaManager/isFullfilledBy renames). The root composer.json no longer influences the result.

This path (composerJsonFilePath set) resolves versions straight from the declared constraints, so it is independent of rector-src#8363 and green on the current released rector-src as well — verified locally, 3/3.