Fix T92962 Boolean output indices unstable.

A parallel loop to create the interesection meshes for each triangle
meant that with parallelism, the output order of the created meshes
could vary with each execution. Keep the parallelism for doing the CDTs
for interesection, but move the extraction of the new faces into a
serial loop afterwards, for repeatability.

Fix T84493 issue with selection after boolean.

According to Blender selection rules, selections should be flushed
to containing elements. Added an EDMB_select_flush() after edit
mode booleans or intersects are done. Hopefully this doesn't break
any scripts that might have been depending on the old (broken) behavior.

Merge branch 'master' into soc-2020-io-performance

Merge branch 'master' into soc-2020-io-performance

Add more regression tests for new obj exporter.

This adds regression tests for exporting most of the blend files
in the io_tests/blend_geometry and io_tests/blend_scene tests.
A fix was necessary in the BlendfileLoadingBaseTest class to prevent
leakage of some global data generated when a loaded file has metaballs.
Also, had to fix the exporter to deal with empty curves.

Merge branch 'master' into soc-2020-io-performance

Fix T91889 Exact boolean sometimes drops triangles.

The problem is that the fast triangulator (based on polyfill)
sometimes makes degenerate triangles. Commit 8115f0c5bd91f had
a check for degenerate triangles but it wasn't thorough enough.
This commit uses a more thorough (and pessimistic) test for
degenerate triangles, using the exact triangulator in those cases.

Fix T91810 Bevel not working well with certain unbeveled edge positions.

A previous commit, c56526d8b68ab, which sometimes didn't drop offsets
into 'in plane' faces, as a fix to T71329, was overly aggressive.
If all the intermediate edges are in the same plane then it is fine
to just put the meeting point on the plane of the start and end edges.

Merge branch 'master' into soc-2020-io-performance

Merge branch 'master' into soc-2020-io-performance