add new all-settled promise handler

[mintybayleaf]

I added a new promise handling function called allSettled historically in most programming languages this function name waits for every promise to finish running (or failing) before performing operations on them.

This is really good for batching activities in a workflow or maybe one child workflows in a workflow

I used this to wait for a batch of activities to run then handle the errors at the end if any exist.

I would like it if I could implement the function in the repository because leveraging the internals of the temporal.promise in the SDK here is a bit nasty to do in our repository.

This is a lot cleaner and could be useful to others (at least I think so)

I implemented the feature like this because of these two examples from the Temporal core team (as maxim suggested)

1. https://github.com/temporalio/samples-java/tree/main/core/src/main/java/io/temporal/samples/batch

2. https://community.temporal.io/t/async-activities-in-workflow/896

SIDE NOTE:

Also fixes a bug in the scheduling code that was not pulling the :schedule key out of the options passed into the schedule like one would assume.