JNI: reuse protocol parameter adapters across overloads - #9

Problem

JNI extraction emits a protocol-parameter adapter for each function declaration. Overloads with the same function name, parameter name, and enclosing type can require the same adapter, so the generated Swift contains duplicate class declarations and fails to compile.

For example, both initializers below generate the same adapter for store:

public protocol Store {
  func value() -> Int64
}

public struct Client {
  public init(store: some Store) {}
  public init(store: some Store, extra: Int64) {}
}

With this change, that adapter is emitted once and both initializers reuse it. The same applies to overloaded instance methods and free functions.

Changes

• Track emitted protocol-parameter adapters for the generator's output batch.
• Reuse an existing adapter when its name and protocol conformances match; assert that a repeated name never silently acquires a different conformance list.
• Keep separate adapters for distinct parameter-wrapper names.
• Add a generator regression that counts adapter declarations for overloaded initializers and free functions, plus Java runtime coverage for overloaded initializers and instance methods using Java callbacks.

Validation

• Confirmed the new generator regression finds two declarations per shared adapter before the fix and one afterward.
• swift test --disable-experimental-prebuilts --disable-sandbox --filter JNIProtocol: 27 tests passed.
• ./gradlew :Samples:SwiftJavaExtractJNISampleApp:test --no-daemon: all Java tests passed, including the new callback round trips.
• swift-format and git diff --check passed.

Tested with Apple Swift 6.4 and JetBrains Runtime 25 on macOS.