fix(elasticsearch): coerce document _id to declared int identifier type

[soyuka]

Summary

Elasticsearch always exposes the document identifier (_id) as a string. DocumentNormalizer::populateIdentifier() wrote that raw string into _source under the resource's identifier key, so a resource whose identifier is declared int failed denormalization in the inner ObjectNormalizer with NotNormalizableValueException (The type of the "id" attribute ... must be one of "int" ("string" given)).

The normalizer now coerces _id to int only when the identifier's declared native type is int (and not string). String and UUID identifiers are left untouched. The coercion is type-driven via PropertyMetadataFactoryInterface::create(...)->getNativeType(), not a blind cast; when the property metadata factory or type info is unavailable the value is returned unchanged (no behavior change).

Reproduction

Denormalizing an ES document with a string _id into a resource whose identifier is ?int threw NotNormalizableValueException instead of building the item.

Test plan

• Added failing test testDenormalizeCoercesIdentifierToDeclaredType (red before fix, green after).
• Full Elasticsearch test suite passes locally.
• php-cs-fixer + PHPStan clean; the container compiles with the new (nullable, last-position, BC-safe) constructor argument.

Fixes #8010