swift-plugin-server: update for throwing SwiftSyntax API (#78114)

Depends on https://github.com/swiftlang/swift-syntax/pull/2915

The `main` method on `CompilerPluginMessageListener` can synchronously clean up resources that cannot be dealt with in a deinitializer due to possible errors thrown during the clean up. Usually this includes closure of file handles, sockets, shutting down external processes and IPC resources set up for these processes, etc.

tools/swift-plugin-server/Sources/swift-plugin-server/swift-plugin-server.swift

@@ -21,6 +21,6 @@ final class SwiftPluginServer {
       connection: connection,
       provider: LibraryPluginProvider.shared
     )
-    listener.main()
+    try listener.main()
   }
 }