Bevel modifier: let it work on wire edges when vertex_only.

Fix T67196: bevel bad at a 3-edge bevel.

The test for whether or not this was a "pipe" neglected to use
fabsf() around a dot result.

Fix T66204, bevel numeric input respect scene units.

Fix T65929: multi-object editing for new normals tools.

Leaving the modal point-at as a TODO for now.
All the rest of the new split normal tools converted to
operate on all selected objects.

Fix T65660 Mirror modifier didn't work with custom normals.

Fix T65141 Bevel did not curve.

The previous fix to the spike bug T64582 was not really right.
This fixes that one properly and restores the desired curving
profile in the bug's example.

Fix T64989 Bevel hangs with Mark Sharp sometimes.

Code for extending sharp edges assumes ADJ pattern and this
example uses TRI_FAN pattern. This change doesn't fix TRI_FAN
mark sharp bug at least won't infinite loop any more.

Fix T64582: bevel spikes sometimes

The code to move the profile plane needed to not do that in
a few more cases.

Normal UI: Make Alt-N shortcut to Normals Menu.

See T64324 for discussion of normals ui.
Consensus on blender.chat was to use Alt-N to pull up Normals Menu,
overwriting the old use of that key (Flip normals).
There are still shortcuts for Recalculate Outside and Recalculate Inside
which are likely the more common needs.

Normal UI: for all ops needing autosmooth on, enable it if needed.

Now Normal menu operations and rotate normals (r n) do not need
manual enabling of autosmooth first.
See T64324 for discussion of Normal UI changes.