Add fallback support to local ideograph font families

[tobrun]

This PR matches logic from #14862 and makes #15225 obsolete. Proposed change allows developers to pass in a array of string for localideographfamily and we will check if we can find a valid font and pass that to core. If not, fallback on sans-serif.

Note: I'm currently not satisfied with taken approach, it uses reflection to lookup valid fonts from TypeFace. Sadly, there isn't an API on the Android SDK to do this cleanly. LMK if you are aware of any.

• optimize for null values, providing a null should result in downloading the fonts.

[tobrun]

While running on Android Q beta 4, I'm seeing:

W/pboxsdk.testap: Accessing hidden field Landroid/graphics/Typeface;->sSystemFontMap:Ljava/util/Map; (greylist, reflection, allowed)

this means that this reflection call is greylisted as is allowed for the time being. Probably because there isn't any other way of checking font avallability outside of the downloadable fonts in https://developers.google.com/fonts/docs/android which requires min api 16 when using the appcompat variant. Long term we will be switching to that setup instead.

[tobrun]

On request from @LukasPaczos also verified that this solution works with https://developer.android.com/guide/topics/ui/look-and-feel/downloadable-fonts

[LukasPaczos]

Looks good, thanks for running additional tests 👍

[ghost]

Hi! Do we have any update on this? I would like to know if and how I can use local fonts on my symbol layers. Thanks!

[LukasPaczos]

Hey @EBiCS, thanks for using Mapbox! This PR references local ideographs generation, which means that the SDK will not download CJK glyphs but rather generate them locally. If you'd like to use a certain font, it has to be declared in your style using Mapbox Studio.