Add bold support for CJK characters

[wangyingfang]

Use system font family to draw characters of CJK, but don't support bold font on iOS. Add similar logic as Android side.

[louwers]

Can't you use a bold font?

[github-actions]

Bloaty Results (iOS) 🐋

Compared to main

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  +0.0%    +176  [ = ]       0    TOTAL

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/bloaty-results-ios/pr-3069-compared-to-main.txt

[louwers]

I don't think matching on the name is a good idea because fonts with 'bold' in the name tend to be bold already!

I think the proper way to implement this would be with a font-weight style spec property. However, I think it's much easier to use a local or server font that is already bold.

[louwers]

I wasn't aware this is exactly what MapLibre Android and MapLibre GL JS do...

[louwers]

I added a test. Please take a look if it looks OK to you.

Also, please have a look at my comments. Thank you.

[github-actions]

Benchmark Results ⚡

Benchmark                                                     Time             CPU      Time Old      Time New       CPU Old       CPU New
------------------------------------------------------------------------------------------------------------------------------------------
OVERALL_GEOMEAN                                            +0.0121         +0.0120             0             0             0             0

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/benchmark-results/pr-3069-compared-to-main.txt

[github-actions]

Bloaty Results 🐋

Compared to main

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  [ = ]       0  [ = ]       0    TOTAL

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/bloaty-results/pr-3069-compared-to-main.txt

Compared to d387090 (legacy)

    FILE SIZE        VM SIZE    
 --------------  -------------- 
   +30% +34.6Mi  +432% +25.8Mi    TOTAL

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/bloaty-results/pr-3069-compared-to-legacy.txt

[random3940]

I find it peculiar that we need to figure out bold flag from the name, but change seems to reflect what Android does and fixes the bug. LTGM.