This reverts commit c7a1e5cd.

Motivation: avoid OpenFlipper crash when saving meshes with unsupported
properties.

Track if garbage collection is necessary.

This is useful for precondition checks in client code.

PR includes the bugfix from !5

See merge request !6

This is useful for precondition checks in client code.

Fix deferred vertex deletion, add unit tests.

GeometryKernel::collect_garbage used to first perform the TopologyKernel
garbage collection, usually shrinking its vertex_deleted_ member, then
accessed it using is_deleted() with the old vertex indices.

This caused out-of-bounds memory access (made visible by
cmake -DSTL_VECTOR_CHECKS=ON) and non-fast deletion also resulted in wrong
results, the remaining vertices had wrong coordinates.

See merge request !4

GeometryKernel::collect_garbage used to first perform the TopologyKernel
garbage collection, usually shrinking its vertex_deleted_ member, then
accessed it using is_deleted() with the old vertex indices.

This caused out-of-bounds memory access (made visible by
cmake -DSTL_VECTOR_CHECKS=ON) and non-fast deletion also resulted in wrong
results, the remaining vertices had wrong coordinates.

Conflicts:
	CI/ci-mac.sh
	VERSION
	src/Unittests/unittests_files.cc

Split unittests into seperate files

Split unittests to avoid huge compile unit

See merge request !1