Add test for mapnik/pull/4556

[astridx]

Add a test for mapnik/mapnik#4556

Note: The second space is slightly wider because it uses Sinhala. So far, via u_ispunct(), we only test punctuation characters (Unicode General Category P). A space belongs to General Category Z. See https://www.unicode.org/reports/tr44/#General_Category_Values (mapnik/mapnik#4555).

We have a license for Noto fonts, so it should be possible to use fonts/Noto/NotoSansSinhalaUI-Regular.ttf.

For the text XML, see:
https://github.com/mapnik/mapnik/blob/73b5a998c3b3474223fe263719ae5cd75bfc2cf4/include/mapnik/text/harfbuzz_shaper.hpp#L293 for the text XML

RUN:[0,1] LANGUAGE:unknown SCRIPT:1517910393(0) Zyyy FONT:Noto Sans
RUN:[1,4] LANGUAGE:en SCRIPT:1281455214(25) Latn FONT:Noto Sans
RUN:[4,6] LANGUAGE:unknown SCRIPT:1517910393(0) Zyyy FONT:Noto Sans
RUN:[6,7] LANGUAGE:en SCRIPT:1281455214(25) Latn FONT:Noto Sans
RUN:[7,13] LANGUAGE:si SCRIPT:1399418472(33) Sinh FONT:Noto Sans
RUN:[7,13] LANGUAGE:si SCRIPT:1399418472(33) Sinh FONT:Noto Sans Sinhala UI
RUN:[13,14] LANGUAGE:unknown SCRIPT:1517910393(0) Zyyy FONT:Noto Sans
RUN:[14,17] LANGUAGE:en SCRIPT:1281455214(25) Latn FONT:Noto Sans
RUN:[17,19] LANGUAGE:unknown SCRIPT:1517910393(0) Zyyy FONT:Noto Sans

I created the test based on https://github.com/mapnik/test-data-visual/blob/master/styles/text-malayalam.xml.