AgnostiqHQ/covalent: v0.60.0

[0.60.0] - 2022-04-06 Changed List type removed from type annotation for the executor argument in electron/lattice/lepton definitions. Input executor argument is converted to an executor class object (if it were a string) in electron/lattice/lepton definitions instead of just before execution in execution.py. As a result, calls to _executor_manager.get_executor are removed from execution.py. Rewritten tests to take into account the type change of executor identifiers from strings to executor class objects. Fixed In covalent/executor/init.py, from importlib import metadata is used instead of importlib.metadata. Electron.get_op_function.rename now uses the correct separator string when renaming a function