Fix T83725 Inconsistent vertex group between exact and fast boolean.

This makes the exact boolean have zero weights for any vertex groups
on any newly created vertices, which is what the fast solver does.

The exact boolean solver was interpolating vertex data when interpolating
loop data in newly created faces. Not sure why I chose that. The Fast
boolean solver doesn't do that, so I stopped doing it too.

Fix T83630 Exact Boolean assert failure in Debug build.

I thought I had reasoned that the add_patch would only happen
when the patch was not already in a cell, but I missed reasoning
about merged cells. So switched to a set 'add' instead of 'add_new'.

Reorder fields in boolean's ITT_value to save memory.

Add more timing hooks for boolean.

Speed up finding patch components in new boolean.

By checking if a cell has already been processed in the finding patch
component code, an enormous speedup happens. This only will be
noticeable if there are lots of patches, and some cells with a
large number of patches.

Speedups for finding cells in new boolean.

In case where there are coplanar instersections where
each part has a lot of triangles, the finding-cells algorithm was
very inefficient. This uses a Set instead of a Vector to keep track
of a cell's patches, avoids going through all patch x patch combinations,
avoids going through all patches to renumber after a merge, and
merges smaller patch-sixe cells into larger ones.
All this reduces the time to find cells in the cited case by a factor of 10.

Add performance timing to mesh_boolean.cc.

You can uncomment the PERFDEBUG define to get timings.

Speedups for new boolean. Better hash function for verts.

The existing hash function didn't work well with Set's method of
masking to the lower bits, because many verts have zeros in the
lower bits.
Also, replaced VectorSet with Set for Vert deduping.

Previous commit forgot to guard some things with #ifdef WITH_GMP.

Improve speed of Constrained Delaunay Triangulation with exact arith.

By using floating point filters, the speed improves by a factor of 2 to 10.
This will help speed up some cases of the Exact Boolean modifier.
Changed the interface of mpq2::isect_seg_seg to not return mu, as it was
not needed and not calculating it saved 15% time.