Introduce a configurable Timezone for improved Advanced Roadmaps for Jira Plans

Improved ARJ plans are implicitly showing all dates in UTC. This may lead to confusion when integrating sprints from boards. Sprints start and end on certain dates and times configured with the timezone associated with their board.

Consider for example a board configured with UTC+10 having a start date set to 1/Jan 1AM. If an issue is assigned to this sprint or scheduled into it by the auto-scheduling function, the associated bar in the visual schedule will show it to start on 31/Dec.
 
Steps: # Create a sprint on UTC +10 timezone in jira.

1. Add the sprint board to a plan.

 
Expected Result:

1. The sprint is displayed with the correct dates on the plan.

 
Actual Result:

1. Sprint dates are used on UTC and do not match the timezone settings resulting in a mismatch from the dates displayed.