Wait for promise to resolve regardless of loop being stopped

[Grinnz]

Summary

Ensure that wait will keep running the loop until the promise is no longer pending.

Motivation

Calling wait can result in a still-pending promise even if the loop is not running, as anything may stop the loop. This small change ensures that it will not return while the promise is pending, which is the documented behavior and user expectation. This is also important for the proposed get method(s), to ensure it does not return before the results are available.

References

Prior art: the implementations of await and get in Future event loop subclasses will loop until the Future is no longer pending.

[kraih]

Wanted to merge this PR, but there are now conflicts.

[Grinnz]

Rebased