Use new api in samples

samples/echoServer/src/echoServerMain/kotlin/EchoServer.kt

@@ -22,7 +22,7 @@ fun main(args: Array<String>) {
     memScoped {
 
         val buffer = ByteArray(1024)
-        val prefixBuffer = "echo: ".toUtf8()
+        val prefixBuffer = "echo: ".encodeToByteArray()
         val serverAddr = alloc<sockaddr_in>()
 
         val listenFd = socket(AF_INET, SOCK_STREAM, 0)

samples/libcurl/src/libcurlMain/kotlin/CUrl.kt

@@ -45,7 +45,7 @@ class CUrl(url: String)  {
 
 fun CPointer<ByteVar>.toKString(length: Int): String {
     val bytes = this.readBytes(length)
-    return bytes.stringFromUtf8()
+    return bytes.decodeToString()
 }
 
 fun header_callback(buffer: CPointer<ByteVar>?, size: size_t, nitems: size_t, userdata: COpaquePointer?): size_t {

samples/videoplayer/src/videoPlayerMain/kotlin/DecoderWorker.kt

@@ -34,7 +34,7 @@ private fun Int.checkAVError() {
     if (this != 0) {
         val buffer = ByteArray(1024)
         av_strerror(this, buffer.refTo(0), buffer.size.convert())
-        throw Error("AVError: ${buffer.stringFromUtf8()}")
+        throw Error("AVError: ${buffer.decodeToString()}")
     }
 }
 

samples/weather_function/function/src/main/kotlin/org/example/weather_func/curl.kt

@@ -91,4 +91,4 @@ fun writeCallback(buffer: CPointer<ByteVar>?, size: size_t, totalItems: size_t,
     return responseSize
 }
 
-private fun CPointer<ByteVar>.toKString(length: Int) = readBytes(length).stringFromUtf8()
+private fun CPointer<ByteVar>.toKString(length: Int) = readBytes(length).decodeToString()