Replace Segoe UI and all Fabric icons with non-licensed alternative

[Arlodotexe]

According to the license here, and the comment here, usage of Segoe UI in projects with FabricUI, and usage of the icons in the library are prohibited unless the application being developed integrates directly with a Microsoft product.

We'll need to find a replacement for Segoe UI (which is currently default for the <Text> control), and an alternative for the fonts. We already have FontAwesome installed, but can add another icon alternative if needed.

[Arlodotexe]

It should be possible to override the icons instead of manually replacing them all:
microsoft/fluentui#3312 (comment)