[windows] Improve Dialog API. Major refactor.

v2/internal/subsystem/call.go

@@ -151,7 +151,7 @@ func (c *Call) processSystemCall(payload *message.CallMessage, clientID string)
 		if err != nil {
 			c.logger.Error("Error decoding: %s", err)
 		}
-		result, err := c.runtime.Dialog.Save(dialogOptions)
+		result, err := c.runtime.Dialog.SaveFile(dialogOptions)
 		if err != nil {
 			c.logger.Error("Error: %s", err)
 		}

v2/internal/subsystem/runtime.go

@@ -3,12 +3,11 @@ package subsystem
 import (
 	"context"
 	"fmt"
-	"strings"
-	"sync"
-
 	"github.com/wailsapp/wails/v2/internal/logger"
 	"github.com/wailsapp/wails/v2/internal/runtime"
 	"github.com/wailsapp/wails/v2/internal/servicebus"
+	"strings"
+	"sync"
 )
 
 // Runtime is the Runtime subsystem. It handles messages with topics starting