Download Organization Basemaps Independent of Web Map

[Will_CulturalFire]

Provide an interface for Field Maps app where users can download basemap packages (and updates to the same package) that are shared to their organization, without choosing a specific web map/offline area. These basemaps can then be used with any web map.

Use cases:

- manage updates to general use offline base data that can be used for an entire region in a single place.

- one large download on user's own schedule vs. bringing in everyone's devices to sideload packages

- provides useful place to host multiple vector styles and allow users to choose between them (ex dark mode, large text)

- reduce duplicated base data across multiple offline areas

[LindsayRaabe_FPCWA]

I wish there was a better way to get basemap packages onto devices besides sideloading them. Sooooooo not conducive to rollouts/updates beyond a few people who reside locally. 

[Jeremy_Z]

Considering how many times we have the same data on different maps, I fully support this. Downloads of large offline areas would be much faster, as well.