[story points] Provide option to hide issues with open PRs

[mcomella]

When checking through sprint progress on the current milestone, we only need to check in on the status of issues that don't have PRs open since those are close to landing. We can provide an option to hide these PRs.

[bbinto]

As a product manager, when reviewing milestones and their current status, I would like to make sure issues with PRs assigned are not being included in the remaining calculator estimate.

They should/can still show up (maybe greyed out or somehow easily visible that they are not included in the remaining calculator).

[mcomella]

This makes sense with the estimate. The calculator is pretty hacky (e.g. with recalculate button) so this might require cleaning it up a bit.