[dagit] State refactor for execution tabs
Summary: Refactor state management for ExecutionTabs, including conversion to hooks. In a followup, I'll be adding a warning dialog for when a tab is going to be removed on the Playground page.
Test Plan: Create and modify tabs in Playground, including config. Navigate away, refresh page, etc, verify that all state is maintained correctly.
Reviewers: bengotow, alangenfeld, prha, sashank
Reviewed By: bengotow, sashank
Differential Revision: https://dagster.phacility.com/D4747