Load tiles using the request stack

[justin-bits]

• Allows requests to be cancelled on layer removal, date change, timeline update, zoom change
• Allows requests to be stubbed in Cypress tests

[justin-bits]

Cypress part of this ticket OBE. Remainder may still be valid.

[schmidtk]

Thanks Justin. The rest we don't want to do for browser caching purposes. This would be much slower than the current approach.