fix: map icon size and resolution

[shrouxm]

Description

I think what is happening here is we're working around a bug in rnmapbox where they ignore the scale attribute of RN ImageSources passed into the Mapbox.Images component on Android only. We do this by selectively multiplying the icon size by the pixel ratio on Android only. I'd like paul to confirm it looks good on his iOS dev setup before merging, but i think we still won't know until we push a release with this fix.

Checklist

• Corresponding issue has been opened

Related Issues

Fixes (hopefully, once QA'd) #192, #367, #316, and #365

Verification steps

Map icons should be the correct size and not pixelated on all platforms.

[shrouxm]

@paulschreiber there are two commits on the branch. the head commit i think should be working properly, but if it isn't try the other commit and make that one the head commit if it works better!