Task delay model

[shital-orchestral]

Added Delay Property as a new field under task properties, with the use of field, we can add delay in-between execution of the tasks. Thanks

[m4dcoder]

@shital-orchestral

1. The value of the task delay can be an expression (string) or an integer. Here is an example where the delay is an expression at https://github.com/StackStorm/st2/blob/master/contrib/examples/actions/workflows/orquesta-delay.yaml#L17. This current PR doesn't load this workflow definition and display the delay value correctly.
2. Is it possible to provide a hint when hover over the delay field which type of values user can input? For example, when hover over delay, hint that user can input an expression or integer.

[m4dcoder]

@shital-orchestral Can you make the delay input box the same as the delay in the task retry model? This will be more consistent.

[amanda11]

LGTM @m4dcoder @shital-orchestral
The only feature I saw from testing was that I can enter -1 for delay, and the UI accepts this. But then when the workflow runs I get an error stating:
TypeError: The value of task delay is not type of integer.",

But I think this problem extends to other places as well, and its difficult to verify in the UI as we support strings for putting in contexts. So I think this is ok.

[amanda11]

I don't seem to get a red box up when I'm in the field and enter -3 for delay.
I get one when I have the field as empty, but when it's a negative number then I don't see any message.

[amanda11]

LGTM - I can see the negative number check now. Not sure if I had the wrong artificact before - but looks good.

[m4dcoder]

@amanda11 Here you go. You should be seeing the error shown in the screenshot.

[amanda11]

LGTM