Fix T75840: Add check for not generated edges

The value of `new_edge` is `SOLIDIFY_EMPTY_TAG=2^32-1` if the edge is not generated.
The code from D7334 was missing this check.

Reviewed By: mont29

Maniphest Tasks: T75840

Differential Revision: https://developer.blender.org/D7463

Fix mistake from last commit to solidify.

While review the behaviour was changed accidentally.
Now Solidify just crashes everytime.

This is the fix for that.

Reviewed By: mont29

Differential Revision: https://developer.blender.org/D7434

Fix crash whith Simple Solidify and Bevel Convex.

After recent changes, simple solidify modifier would crash with Fill Rim
turned off and Bevel Convex emabled.

Also fixes that simple solidify would not set the bevel weight flag so the
next modifier could use the bevel weights.

Simple cleanup with do_rim is also included.

Reviewed By: mont29

Differential Revision: https://developer.blender.org/D7428

Add Complex Solidify option for thickness per face

Add an option to solidify complex which will make faces which have thickness
controlled by vertex weights flat/even, and parallel to their original face.

For each face it uses the minimal weight assigned to its vertices to control
the thickness.

This will help users for example in architecture or basic CAD design by finally
making solidify work there at all if altering thickness is needed.

Differential Revision: https://developer.blender.org/D7340

Reviewed and minor cleanups by Batien Montagne (@mont29).

Improve Solidify/Bevel Modifier cooperation

Adds a slider to solidify which allows the user to add bevel weight on the outside
or remove bevel weight from the inside.

Also includes a very small improvment for working with subsurface modifier where
the rim edge in complex solidify will now also have a chance to get a crease if
there is only two adjacent edges.

Differential Revision: https://developer.blender.org/D7334

Reviewing and minor cleanups: Bastien Montagne (@mont29).

Fix T75032: New complex solidify algorithm handles poorly merging threshold of small geometry details.

* Implemented the algortihm that would merge vertices to the weighted
center between them.
* Exposed the merge threshold to the user.

The new default tolerance is 0.0001 (versionning code ensures that
previous default value remains in use to avoid any change in existing
files).

Review and minor changes/cleanups from Bastien Montagne (@mont29).

Fix missing Surface Deform strength versioning

Screw Modifier: support 1-2 steps

The Screw Modifier had a lower limit for the steps value, which not only
was inconsistent between render and viewport steps, but also was capped
to 2 in UI and also in the code internally.

Fix solidify complex degenerate cases with duplicate faces

The removal of duplicate faces that are created during the handling of
degenerate cases was implemented already but didn't work.
This patch should fix some crashes with the solidify complex mode
related to that.

See D7221 for details.

Change solidify's material offset in complex mode to conform with simple mode

this patch will change the behaviour of the material offset in complex mode to fit simple mode output.
Previously in complex mode this would offset the material of the enire shell,
because when you read the tooltip it says material for new generated geometry.
In complex mode everything is new generated geometry though.
In simple mode on the other hand, this would give you a way to only change the inside faces
material. There may be cases in large modifier stacks where material offset like it is implemented
currently in complex mode may be useful, but it is much more useful in the way it is implemented
by simple mode.

Reviewed By: mont29

Differential Revision: https://developer.blender.org/D7215