fix(playground): persist bottom sheet collapsed state

[sundram-bruno]

JIRA : BRU-4083

Problem

• In the bottom view of the playground, collapsing the sheet and refreshing did not keep it collapsed. It reopened at the last persisted expanded height.
• After dragging the bottom view to a custom height and collapsing it, clicking Try it reopened the sheet at the default 60% height instead of the persisted height, and also overwrote the persisted height with the default.

Solution

• The collapsed state is now persisted in sessionStorage, so a refresh keeps the sheet collapsed. Expanding it afterwards restores the last expanded height.
• Every expand path (the expand button and the Try it button) now restores the persisted height instead of the default, and the persisted height is no longer overwritten.