Add Android demo for speaker recognition (#536)

See pre-built Android APKs at 
https://k2-fsa.github.io/sherpa/onnx/speaker-identification/apk.html

kotlin-api-examples/Main.kt

@@ -7,11 +7,67 @@ fun callback(samples: FloatArray): Unit {
 }
 
 fun main() {
+  testSpeakerRecognition()
   testTts()
   testAsr("transducer")
   testAsr("zipformer2-ctc")
 }
 
+fun computeEmbedding(extractor: SpeakerEmbeddingExtractor, filename: String): FloatArray {
+    var objArray = WaveReader.readWaveFromFile(
+        filename = filename,
+    )
+    var samples: FloatArray = objArray[0] as FloatArray
+    var sampleRate: Int = objArray[1] as Int
+
+    val stream = extractor.createStream()
+    stream.acceptWaveform(sampleRate = sampleRate, samples=samples)
+    stream.inputFinished()
+    check(extractor.isReady(stream))
+
+    val embedding = extractor.compute(stream)
+
+    stream.release()
+
+    return embedding
+}
+
+fun testSpeakerRecognition() {
+    val config = SpeakerEmbeddingExtractorConfig(
+        model="./3dspeaker_speech_eres2net_large_sv_zh-cn_3dspeaker_16k.onnx",
+        )
+    val extractor = SpeakerEmbeddingExtractor(config = config)
+
+    val embedding1a = computeEmbedding(extractor, "./speaker1_a_cn_16k.wav")
+    val embedding2a = computeEmbedding(extractor, "./speaker2_a_cn_16k.wav")
+    val embedding1b = computeEmbedding(extractor, "./speaker1_b_cn_16k.wav")
+
+    var manager = SpeakerEmbeddingManager(extractor.dim())
+    var ok = manager.add(name = "speaker1", embedding=embedding1a)
+    check(ok)
+
+    manager.add(name = "speaker2", embedding=embedding2a)
+    check(ok)
+
+    var name = manager.search(embedding=embedding1b, threshold=0.5f)
+    check(name == "speaker1")
+
+    manager.release()
+
+    manager = SpeakerEmbeddingManager(extractor.dim())
+    val embeddingList = mutableListOf(embedding1a, embedding1b)
+    ok = manager.add(name = "s1", embedding=embeddingList.toTypedArray())
+    check(ok)
+
+    name = manager.search(embedding=embedding1b, threshold=0.5f)
+    check(name == "s1")
+
+    name = manager.search(embedding=embedding2a, threshold=0.5f)
+    check(name.length == 0)
+
+    manager.release()
+}
+
 fun testTts() {
   // see https://github.com/k2-fsa/sherpa-onnx/releases/tag/tts-models
   // https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/vits-piper-en_US-amy-low.tar.bz2