Skip @AutoConfigureWebTestClient when WebTestClient is built manually

[MBoegers]

What's changed

AddAutoConfigureWebTestClient adds @AutoConfigureWebTestClient to @SpringBootTest tests that reference WebTestClient. However, when a test builds its WebTestClient manually — e.g. WebTestClient.bindToServer().build() — the bean is not auto-configured, so the annotation is unnecessary. Worse, adding it (and its import) requires the org.springframework.boot:spring-boot-webtestclient artifact, which may not be on the classpath, breaking compilation.

This PR guards the recipe with an additional precondition so the annotation is only added when WebTestClient is not constructed manually:

not(new UsesMethod<>("org.springframework.test.web.reactive.server.WebTestClient.MockServerSpec build()", true))

The check assumes a test either creates all of its WebTestClient instances manually or none of them.

Why

Reported while validating UpgradeSpringBoot_4_0 on a customer multi-module migration: the recipe added @AutoConfigureWebTestClient to a manually-configured test, introducing a org.springframework.boot.webtestclient.autoconfigure import for a package that wasn't available, which broke compilation of an already-SB4 module.

• This partially addresses the WebTestClient gap (Gap 2) from moderneinc/customer-requests#2572. It does not add the spring-boot-webtestclient dependency for the cases where the annotation is legitimately added — that remains open.

Testing

Added shouldNotAddAnnotationIfConfiguredManual covering the manual-build case, and extended the WebTestClient test stub with bindToServer() / MockServerSpec so the call chain has proper type attribution. All tests in AddAutoConfigureWebTestClientTest pass.

• Partially fixes moderneinc/customer-requests#2572 — addresses Gaps 1 and 2.