Allow user preference to control date renderer formats

[amcclain]

A client would like to support a built-in appwide option to swap date rendering between current ISO yyyy-mm-dd and US-style mm/dd/yyyy.

Given how centralized our date rendering is, this seems like it could be accomplished without too much effort, BUT comes with the big caveat that developers might be relying on those formatters to produce strings for comparison or formatting dates to post to APIs. Ideally those usages would be more defined, but it's something to consider and think through how we could communicate and potentially provide additional versions of the formatters that are preset to the ISO format and specify as much in the name.