Thunk retry options and other supervisors

This may or may not make sense at the Dagger level, but for consideration - as an example copying the [prefect ](https://docs.prefect.io/core/tutorial/04-handling-failure.html#if-at-first-you-don-t-succeed)keywords below

```julia
import Dates
import Dagger

function flaky_function()
# accesses some network resource that could fail
end

res = Dagger.@spawn max_retries=3 retry_delay=Dates.Minute(1) flaky_function()
```