936/reenable test region

[Jaapel]

Issue addressed

Fixes #936

Explanation

• Fixed a PerformanceWarning by refactoring vector merge
• Changed assertions for different region methods
• Changed the world fixture as the .geojson was corrupted.

General Checklist

• [x] Updated tests or added new tests
• [x] Branch is up to date with v1
• [x] Tests & pre-commit hooks pass
• [x] Updated documentation
• [x] Updated changelog.rst

[Jaapel]

@deltamarnix @hboisgon not sure what to do with the region test failing. The region parse_region functions seem very differently from the previous tests: https://github.com/Deltares/hydromt/blob/v0.9.4/tests/test_basin_mask.py#L81

[Jaapel]

@DirkEilander can you help debug the XY coordinates outside of domain exception?