Android XRay (#840)

* Add XRay module

client/android/xray/src/main/kotlin/XrayConfig.kt

@@ -0,0 +1,42 @@
+package org.amnezia.vpn.protocol.xray
+
+import org.amnezia.vpn.protocol.ProtocolConfig
+import org.amnezia.vpn.util.net.InetNetwork
+
+private const val XRAY_DEFAULT_MTU = 1500
+private const val XRAY_DEFAULT_MAX_MEMORY: Long = 50 shl 20 // 50 MB
+
+class XrayConfig protected constructor(
+    protocolConfigBuilder: ProtocolConfig.Builder,
+    val socksPort: Int,
+    val maxMemory: Long,
+) : ProtocolConfig(protocolConfigBuilder) {
+
+    protected constructor(builder: Builder) : this(
+        builder,
+        builder.socksPort,
+        builder.maxMemory
+    )
+
+    class Builder : ProtocolConfig.Builder(false) {
+        internal var socksPort: Int = 0
+            private set
+
+        internal var maxMemory: Long = XRAY_DEFAULT_MAX_MEMORY
+            private set
+
+        override var mtu: Int = XRAY_DEFAULT_MTU
+
+        fun setSocksPort(port: Int) = apply { socksPort = port }
+
+        fun setMaxMemory(maxMemory: Long) = apply { this.maxMemory = maxMemory }
+
+        override fun build(): XrayConfig = configBuild().run { XrayConfig(this@Builder) }
+    }
+
+    companion object {
+        internal val DEFAULT_IPV4_ADDRESS: InetNetwork = InetNetwork("10.0.42.2", 30)
+
+        inline fun build(block: Builder.() -> Unit): XrayConfig = Builder().apply(block).build()
+    }
+}