[m-stephen]

Closes: #14470
Closes: #14866

Fixed an issue that caused the map to ignore the remote fonts for CJK Kanji glyphs.
Added ability to specify an array of fonts for fallbacks for local ideographic font family.

After this PR merged, we will:

1. Enabled local font rendering for CJK glyph as default for accelerating map’s loading, using Apple system default font.
2. If developers set MGLIdeographicFontFamilyName to a string value, which is a custom local font family name, e.g. PingFang TC, we will use that for local rendering.
3. If developers set MGLIdeographicFontFamilyName to an array of local fonts' family name, we will choose the first available font of that array. If there isn't an available font name, fallback to system default font.
   For example, we will use PingFang TC as a local font:

	<key>MGLIdeographicFontFamilyName</key>
	<array>
		<string>Test</string>
		<string>Test2</string>
		<string>PingFang TC</string>
		<string>Arial</string>
	</array>

4. If developers set MGLIdeographicFontFamilyName to a boolean value of NO, we will use their remote CJK font.

[m-stephen]

FYI, I also found another issue, we cannot render the Hiragana or Katakana using local font, this is the deep reason why we cannot display Japanese characters well:

We use local font in:

mapbox-gl-native/platform/darwin/src/local_glyph_rasterizer.mm

Lines 98 to 100 in df062af

	bool LocalGlyphRasterizer::canRasterizeGlyph(const FontStack&, GlyphID glyphID) {
	return util::i18n::allowsFixedWidthGlyphGeneration(glyphID) && impl->getFont();
	}

and in

mapbox-gl-native/src/mbgl/util/i18n.cpp

Lines 416 to 419 in d7fa18e

	bool allowsFixedWidthGlyphGeneration(char16_t chr) {
	// Mirrors conservative set of characters used in glyph_manager.js/_tinySDF
	return isInCJKUnifiedIdeographs(chr) || isInHangulSyllables(chr);
	}

we judge characters whether can rasterize or not.

The isInCJKUnifiedIdeographs is defined by:

mapbox-gl-native/src/mbgl/util/i18n.cpp

Line 141 in d7fa18e

DEFINE_IS_IN_UNICODE_BLOCK(CJKUnifiedIdeographs, 0x4E00, 0x9FFF)

The unicodes range is from 4E00 to 9FFF, which means we only render Chinese characters using local font. We should add more ranges of CJK glyphs unicodes, and different range of them should use different Apple default font, same as Apple do.

I’ll make a new commit to fix this issue and need GL team help to review.

[m-stephen]

@friedbunny I have added some plist value tests, please re-review, thanks!

[friedbunny]

Thanks for your patience throughout the process, @m-stephen. 🙇