ui: update draggable list ux

[Forfold]

Description:

• Updates flatlist drag and drop UX
• Updates Escalation Policy Steps List to use FlatList

Which issue(s) this PR fixes:
For significant amounts of work, it is best to start an issue first, preferably before the work is started.
For large pull requests, be sure to reference the associated GitHub issue(s).

Usage: Fixes #<issue number>, or Fixes (paste link of issue).

Out of Scope:

• The caching update logic for steps flickers for a moment before "sticking"

Screenshots:

[allending313]

LGTM!

cypress test failing

[mastercactapus]

A couple quick questions:

• Is the flicker a regression introduced in this change or an existing bug?
• Are these still keyboard accessible?

[Forfold]

@mastercactapus The flicker is introduced for Escalation Policies as it is using the same caching logic but a new drag and drop library. It is probably for the best to address that as a follow-up ticket.

They are both still keyboard accessible (this is what the tests cover).

[Forfold]

@mastercactapus I copied over the logic from rotation's optimistic update and it didn't flicker 🎉 so, thanks for calling it out 😄 It should be fixed now.

[andrewbenington]

works smoothly for me!