[DB-7644] Storefront 2.1 release "fit and finish" items

* Ensure well metrics don't overlap labels (give them an opaque
background)
* Highlight the TE to which each Storefront instance is currently
connected
* Remove instant purchaser workload
* Include instructions for running second TE in single-host scenario
(via template modification)
* Include instructions for running second Storefront instance via
command line on multi-tenancy tour
* Keep "add products" button visible even if products exist so more
products can be added
* Add faux progress bars on db create and product create submissions
* Postpone region and host slider updates while user input and
subsequent processing is in progress (to prevent jitter)