Enforce all Unicode Points to be within Private Use Area

[robloo]

Unicode defines private use areas which are used for symbol fonts such as this. Microsoft's other symbol fonts such as Segoe MDL2 Assets and Segoe Fluent Icons follow the private use area ranges correctly. However, this repository for the Fluent UI System does not. Not staying within the private use area causes a lot of issues on certain platforms. Android is known not to process U+FE26 correctly for example.

What is needed is a Breaking Change to several Unicode points pushing them into the ranges below. This is almost mandatory for wide adoption as far as I'm concerned. The built-in .ttf fonts aren't even correct as-is (#299).

https://en.wikipedia.org/wiki/Private_Use_Areas

I will likely have the tooling shortly to correct this. Would appreciate someone from Microsoft to reach out so we can correct this though. Obviously, remapping the glyphs to other Unicode points is a breaking change but it's required as this font is supposed to be usable on Android and iOS. Again, Android is known not to work with certain glyphs.