BackendSrv: Cancellable requests & Observable all the way (#25746)

* BackendSrv: Observable all the way POC

* starting to unify code paths

* tests pass

* Unified error handling

* Single request path and error handling

* Fixed ts issue

* another ts issu

* Added back old requestId cancellation

* Slow progress trying to grasp the full picture of cancellation

* Updates

* refactoring

* Remove a bunch of stuff from backendSrv

* Removed another function

* Do not show error alerts for data queries

* Muu

* Updated comment

* fixed ts issue

* unify request options type

* Made query inspector subscribe to backendSrv stream instead of legacy app events

* Add back support for err.isHandled to limit scope

* never show success alerts

* Updated tests

* Fixing tests

* Minor weak

* Improved logic for the showErrorAlert and showSuccessAlert boolean flags, now they work more logically

* Fix issue

public/app/features/dashboard/components/FolderPicker/FolderPickerCtrl.ts

@@ -8,6 +8,7 @@ import { backendSrv } from 'app/core/services/backend_srv';
 import { ValidationSrv } from 'app/features/manage-dashboards';
 import { ContextSrv } from 'app/core/services/context_srv';
 import { promiseToDigest } from '../../../../core/utils/promiseToDigest';
+import { createFolder } from 'app/features/manage-dashboards/state/actions';
 
 export class FolderPickerCtrl {
   initialTitle: string;
@@ -111,7 +112,7 @@ export class FolderPickerCtrl {
     }
 
     return promiseToDigest(this.$scope)(
-      backendSrv.createFolder({ title: this.newFolderName }).then((result: { title: string; id: number }) => {
+      createFolder({ title: this.newFolderName }).then((result: { title: string; id: number }) => {
         appEvents.emit(AppEvents.alertSuccess, ['Folder Created', 'OK']);
 
         this.closeCreateFolder();