Plugins: Modify interface for plugin validations to allow taking PDC into account (#96089)

* Request interceptor: Do not block PDC

* Apply change after feedback received

* Add test

* Check if secure socks proxy configured for the instance

* Apply suggestions from code review

* Add dedicated service for datasource request URL validation (#99179)

---------

Co-authored-by: Will Browne <wbrowne@users.noreply.github.com>

pkg/services/datasources/service/datasource.go

@@ -745,7 +745,7 @@ func (s *Service) httpClientOptions(ctx context.Context, ds *datasources.DataSou
 		}
 	}
 
-	if ds.JsonData != nil && ds.JsonData.Get("enableSecureSocksProxy").MustBool(false) {
+	if ds.IsSecureSocksDSProxyEnabled() {
 		proxyOpts := &sdkproxy.Options{
 			Enabled: true,
 			Auth: &sdkproxy.AuthOptions{