Remove deprecated analysis_getReachableSources method

[ranbeuer]

Summary

---

• Remove the deprecated analysis_getReachableSources(String file, GetReachableSourcesConsumer consumer);
  declaration from AnalysisServer.
• Remove its corresponding no-op override from RemoteAnalysisServerImpl.
• Eliminate the related deprecated API warning from the IntelliJ Plugin Verifier reports.

---

Verification

The following commands completed successfully:

• ./gradlew buildPlugin
• ./gradlew :test --tests "com.jetbrains.lang.dart.*"
• ./gradlew :test --tests "com.jetbrains.dart.*" -PverboseTests
• ./gradlew verifyPlugin
• ./gradlew verifyPluginProjectConfiguration
• ./gradlew verifyPluginSignature
• ./gradlew verifyPluginStructure

The analysis_getReachableSources warning is no longer present in the Plugin Verifier reports for IU-253, IU-261, or IU-262.

Screenshots are not applicable because this change does not affect the UI.

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[gemini-code-assist]

Code Review

This pull request removes the deprecated 'analysis_getReachableSources' method from the 'AnalysisServer' interface and its implementation in 'RemoteAnalysisServerImpl'. The reviewer recommends completing the cleanup by removing the now-unused 'GetReachableSourcesConsumer' import and deleting the obsolete 'GetReachableSourcesConsumer.java' file.

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third_party/thirdPartySrc/analysisServer/com/google/dart/server/internal/remote/RemoteAnalysisServerImpl.java (334-337)

[CONCERN] Removing the analysis_getReachableSources method makes the GetReachableSourcesConsumer interface and its import on line 41 of this file obsolete. Please remove the unused import and delete the GetReachableSourcesConsumer.java file to complete the cleanup.