GDAL 3.0 compatibility and testing

We need to test compatibility and tests with GDAL 3.

Release 6.6.x already partially tested and fixed (!479 (merged)). For develop we need to:

• Patch .Fixup() !480 (merged)
• Fix importFromWkt warnings (see discussion in #1891 (comment 78228))
• Run all tests (if possible on dashboard / CI)