beef up runtime styling test cases

[incanus]

On both iOS and Android in-repo test apps, we currently test:

• Source/layer addition (GeoJSON, raster)
• Existing Studio-made layer style changes (colors, antialiasing, widths)

However, we don't yet exercise filters, which would have revealed #6233 earlier.

I'm still possibly seeing an issue with filters and styling of existing layers even after #6233 was fixed, so rather than build a test case, I'm going to add one to the framework app.

/cc @ivovandongen @frederoni @jfirebaugh

[jfirebaugh]

If you want to get really beefy, we could write a harness that can execute the test-suite runtime styling tests against the platform SDK APIs.

[incanus]

Apparently the subject line wasn't enough to auto-close, so: got this in #6433 with b846f54.

[incanus]

Re: test harness @jfirebaugh, will keep this in mind as we continue to near runtime styling release.