Add HTTP QUERY method support (RFC 10008)

[kumarprabhashanand]

RFC 10008 defines QUERY as a safe, idempotent, cacheable HTTP method that carries a request body describing query criteria - a body carrying counterpart to GET.

Core

• Request.HttpMethod.QUERY(true) registered as a first-class method
• RequestLine Javadoc updated to list QUERY as a valid method name

Mock client

• feign.mock.HttpMethod gains a QUERY constant; without it, RequestKey.create(Request) threw IllegalArgumentException on any QUERY request routed through MockClient
• MockClientTest adds queryMock() to verify end-to-end routing

Client tests

• AbstractClientTest adds a query() test verifying that QUERY transmits a body with the correct Content-Type and Content-Length
• DefaultClientTest overrides query() to assert RetryableException wrapping ProtocolException - HttpURLConnection.setRequestMethod does not accept QUERY (mirrors the existing PATCH pattern)
• GoogleHttpClientTest and AbstractJAXRSClientTest override query() for the same reason (both delegate to HttpURLConnection under the hood)

HTTP cache

• HttpCacheInterceptor includes QUERY in its default cacheable set
• Cache key incorporates Arrays.hashCode(body) when a request body is present to reduce cross-body collisions
• HttpCacheInterceptorTest verifies that distinct bodies produce separate cache entries and that same-body repeats trigger conditional revalidation

Out of scope: Accept-Query response header (RFC 10008 §6) is not implemented; servers indicate QUERY support via Allow already.