[lldb] [Utility/UriParser] Replace port==-1 with llvm::None

Use llvm::Optional<uint16_t> instead of int for port number
in UriParser::Parse(), and use llvm::None to indicate missing port
instead of a magic value of -1.

Differential Revision: https://reviews.llvm.org/D112309

lldb/source/Plugins/Platform/Android/PlatformAndroid.cpp

@@ -155,7 +155,7 @@ Status PlatformAndroid::ConnectRemote(Args &args) {
   if (!m_remote_platform_sp)
     m_remote_platform_sp = PlatformSP(new PlatformAndroidRemoteGDBServer());
 
-  int port;
+  llvm::Optional<uint16_t> port;
   llvm::StringRef scheme, host, path;
   const char *url = args.GetArgumentAtIndex(0);
   if (!url)