* 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
* DataSourceWithBackend: Switch to new Observable fetch api
* 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
* use ovservable in test
* remove processResponse
* remove processResponse
* trying to get tests to pass :(
* no need for the extra tests
* Fixed processsing
* Fixed tests
* Updated tests to mock fetch call
* lint fixes
Co-authored-by: Ryan McKinley <ryantxu@gmail.com>