http4k - upgrade core library and update server worker count for undertow implementation (#7970)

* update undertow server workers

* upgrade http4k library

frameworks/Kotlin/http4k/build.gradle

@@ -1,6 +1,6 @@
 buildscript {
     ext.kotlin_version = "1.8.10"
-    ext.http4k_version = "4.37.0.0"
+    ext.http4k_version = "4.39.0.0"
 
     repositories {
         mavenCentral()

frameworks/Kotlin/http4k/undertow/src/main/kotlin/Http4kUndertowServer.kt

@@ -13,7 +13,7 @@ private fun CustomUndertow(port: Int) = object : ServerConfig {
         val server = io.undertow.Undertow.builder()
             .addHttpListener(port, "0.0.0.0")
             .setHandler(BlockingHandler(Http4kUndertowHttpHandler(http)))
-            .setWorkerThreads(32 * Runtime.getRuntime().availableProcessors())
+            .setWorkerThreads(64 * Runtime.getRuntime().availableProcessors())
             .build()
 
         override fun start() = apply { server.start() }