test: add remaining tests for all components to increase the coverage

[Maxel01]

This PR primarily adds more tests and improves the overall coverage:

• it is now possible to change the props multiple times to test the reactivity system.
• tests the exports of the library.

on the other side it:

• deprecates 'unreachable' code, which seems that can't be used (geoJSON.ts, gridLayer.ts, imageOverlay.ts, polygon.ts, polyline.ts) -> this needs additional checks before removing.
• does not cover tests for experimental features as they are experimental
• does not cover the full functionality of all functions.