AgnostiqHQ/covalent: v0.25.2

[0.25.2] - 2022-02-21 Changed backend metadata name changed to executor. _plan_workflow usage updated to reflect how that executor related information is now stored in the specific executor object. Updated tests to reflect the above changes. Improved the dispatch cancellation test to provide a robust solution which earlier took 10 minutes to run with uncertainty of failing every now and then. Removed Removed TaskExecutionMetadata as a consequence of removing execution_args