Add FolderUID for library elements (#79572)

* Add FolderUID in missing places for libraryelements

* Add migration for FolderUID in library elements table

* Add Folder UIDs tolibrary panels

* Adjust dashboard import with folder uid

* Fix lint

* Rename back FolderUID to UID

* Remove default

* Check if folderUID is nil

* Add unique indes on org_id,folder_uid,name and kind

* Update pkg/services/libraryelements/database.go

Co-authored-by: Sofia Papagiannaki <1632407+papagian@users.noreply.github.com>

* Fix folder integration test, with unique index on library elements

* Make folder uids nullable and rewrite migration query

* Use dashboard uid instead of folder_uid

* Adjust test

---------

Co-authored-by: Sofia Papagiannaki <1632407+papagian@users.noreply.github.com>

pkg/services/libraryelements/writers.go

@@ -82,6 +82,7 @@ type FolderFilter struct {
 func parseFolderFilter(query model.SearchLibraryElementsQuery) FolderFilter {
 	folderIDs := make([]string, 0)
 	folderUIDs := make([]string, 0)
+	// nolint:staticcheck
 	hasFolderFilter := len(strings.TrimSpace(query.FolderFilter)) > 0
 	hasFolderFilterUID := len(strings.TrimSpace(query.FolderFilterUIDs)) > 0
 
@@ -100,6 +101,7 @@ func parseFolderFilter(query model.SearchLibraryElementsQuery) FolderFilter {
 
 	if hasFolderFilter {
 		result.includeGeneralFolder = false
+		// nolint:staticcheck
 		folderIDs = strings.Split(query.FolderFilter, ",")
 		metrics.MFolderIDsServiceCount.WithLabelValues(metrics.LibraryElements).Inc()
 		// nolint:staticcheck