Added mvt-fixtures' real-world integration tests

[brunoabinader]

Adds real-world integration tests with data coming from https://github.com/mapbox/mvt-fixtures:

• real-world/bangkok
• real-world/chicago
• real-world/nepal
• real-world/norway
• real-world/sanfrancisco
• real-world/uruguay

Changes were made in the integration test HTTP server:

• Added extra /node_modules path mount (for finding .mvt files from the mvt-fixtures node module)
• Resolve local:// URLs also for source tiles field (if used instead of url)

The tests' styles are all based in basic-v9, with slight changes:

• In all tests, the mapbox source tiles field is unique for each test (because the .mvt files are stored in separate folders)
• For Bangkok, the fonts were all replaced to NotoCJK because these provide the extra glyphs
• For all tests containing terrain, a custom contour layer was added (missing in basic-v9 style)

[brunoabinader]

Possible improvements include:

• Hillshading layers
• Complex styles (e.g. similar to streets-v9, but openly available)

[brunoabinader]

I've run these tests in GL native, and so far only tests that show road labels have failed - see e.g. Bangkok:

GL JS	GL native	diff

As pointed out by @ChrisLoer, there is a similar issue tracking label positioning diffs in mapbox/mapbox-gl-native#10412.

[jfirebaugh]

👍
There are several existing tests that use local://../../node_modules/... URLs. Please update these to use local://node_modules/... as well.

[brunoabinader]

@jfirebaugh I ended up using Map's transformRequest instead of transforming URLs on the HTTP server - much simpler, and also enabled us to clean up the remaining ../../node_modules entries.

[mapsam]

@brunoabinader just seeing this for the first time - awesome work! Lemme know if you have any issues with mvt-fixtures, happy to help with updates.

[brunoabinader]

Thanks @mapsam :)