Fix RemoveDependency.unlessUsing for multi-module Maven projects

[steve-aom-elliott]

Summary

RemoveDependency's unlessUsing guard is per-JavaProject marker, which corresponds to a single Maven module. In a multi-module reactor the parent pom carries a different JavaProject than its children, so type usages found in child modules never gate removal from the parent pom — the <dependency> gets stripped from the parent while child modules still rely on inheriting it, producing surprise compile errors in downstream builds.

This came up while looking into a Spring Boot 4 migration failure where io.moderne.java.spring.boot4.MigrateSpringRetry (which calls RemoveDependency: unlessUsing: org.springframework.retry..* at the end of its recipe list) removed spring-retry from a parent pom even though child modules contained extensive RetryTemplate/RetryPolicy/BackOffPolicy usage.

Two commits:

1. Fix RemoveDependency.unlessUsing for multi-module Maven projects — scanner now also records MavenResolutionResult.id -> JavaProject. When the visitor is about to remove from a pom, it walks MavenResolutionResult.getModules() recursively and preserves the dep if any descendant's JavaProject shows the type in use.
2. Allow RemoveDependency to remove ancestor decl when descendants self-declare — refines the descendant check: a descendant only blocks removal if it uses the type AND does not redeclare the dep directly. A descendant that self-declares is self-sufficient, so the ancestor's declaration is dead weight. The self-declaration check uses the raw Pom.getRequested().getDependencies() rather than the resolved/inherited list, so a child that inherits the dep from the very ancestor we're modifying still correctly blocks removal.

Test plan

Five new tests in RemoveDependencyTest (all passing):

• doNotRemoveSpringRetryWhenRetryTemplateInUse — single module, body usage → preserved
• doNotRemoveSpringRetryWhenOnlyImportsPresent — single module, imports only → preserved
• doNotRemoveSpringRetryWhenDepAndUsageInSameChildModule — multi-module, dep + Java in same child → preserved
• doNotRemoveSpringRetryInMultiModuleWhenChildUsesIt — previously failing, parent has dep, child uses → preserved
• removeParentDependencyWhenChildSelfDeclaresAndUses — parent has dep, child redeclares and uses → parent dep removed (commit 2 behavior)

Existing tests continue to pass.