Add callback function to electron

[xjf729]

What should we add?

Discussed in #1673

Now, electron have call_after hooks, which means electron can do something after electron completed successfully. However, there isn't some hooks to let electron do something when status of electron is Failed or Cancelled. Maybe there should have some callback hooks for electron when it is failure or cancelled.

Describe alternatives you've considered.

There is a suggested UX to use callback hooks.

UX

def call_before_hook(value):
    Path("data.txt").write_text(value)
    return value

def call_after_hook():
    Path("data.txt").unlink()

# Remove `data.txt` when `get_my_value_completed` is completed. It has been archieved by `Covalent`. 
# ref: https://covalent.readthedocs.io/en/latest/how_to/coding/add_callable_dependencies_to_electron.html
@ct.electron(
    call_before=ct.DepsCall(call_before_hook, args=(1, )),
    call_after=ct.DepsCall(call_after_hook),
)
def get_my_value_completed():
    value = Path("data.txt").read_text()
    return int(value)

# Remove `data.txt`, regardless of the status of `get_my_value`. It uses new `call_finally` hook.
@ct.electron(
    call_before=ct.DepsCall(call_before_hook, args=(1, )),
    call_finally=ct.DepsCall(call_after_hook),
)
def get_my_value_finally():
    value = Path("data.txt").read_text()
    return int(value)

# Remove `data.txt` when `get_my_value` is cancelled. It uses new `call_after_cancelled` hook
@ct.electron(
    call_before=ct.DepsCall(call_before_hook, args=(1, )),
    call_after_cancelled=ct.DepsCall(call_after_hook),
)
def get_my_value_cancelled():
    value = Path("data.txt").read_text()
    return int(value)

This example will create a file named data.txt, and when function get_my_value* goes to a certain status, data.txt will be removed.