Allow 0 time timedeltas, fix serialize to allow passing timedelta par…

[kierkegaard13]

…ams to subtasks

This PR primarily fixes the serialize function for TimeDeltaParameters to allow passing the parameter to a subtask that is required or yielded in the run function. It also allows creating a parameter with 0 time, which helps with setting defaults.

Description

This is to address problems raised in issue #1966

Motivation and Context

This is to address problems raised in issue #1966

Have you tested this? If so, how?

I have included unit tests and tested it working on another project

[mention-bot]

@kierkegaard13, thanks for your PR! By analyzing the history of the files in this pull request, we identified @eepstein, @Tarrasch and @erikbern to be potential reviewers.

[Tarrasch]

Great job! But I see no tests for the serialization that you fixed. :)

[kierkegaard13]

@Tarrasch my bad. I just added them. Hypothesis didn't have a timedelta strategy that I could see, so I wrote some manual test cases if that's okay. Let me know if there are any others you'd like to see.

[Tarrasch]

@kierkegaard13. Looks good. But could you just move out the test to the same parameter_tests.py file? I think there are already tests (without hypothesis) related to serialization in there.

[kierkegaard13]

@Tarrasch done.

[kierkegaard13]

@Tarrasch think the build stalled. Are you able to restart it, or should I just close and open the PR?

[Tarrasch]

Thanks @kierkegaard13! :)