Merge branch 'blender-v2.81-release'

Fix assert and memleak in recent Skin Root Display patch

Caused by 4ddf3215a7df

Merge branch 'blender-v2.81-release'

Fix T70249 EEVEE: Light bleeding on SSS translucency

This was caused by 2 things: Shadow map bias and aliasing.

It made the expected depth of the shadowmap further than the surface
itself in some cases. In normal time this leads to light leaking on normal
shadow mapping but here we need to always have the shadowmap depth above
the shading point.

To fix this, we use a 5 tap inflate filter using the minimum depth of all
5 samples. Using these 5 taps, we can deduce entrance surface derivatives
and there orientation towards the light ray. We use these derivatives to
bias the depth to avoid wrong depth at depth discontinuity in the shadowmap.

This bias can lead to some shadowleaks that are less distracting than the
lightleaks it fixes.

We also add a small bias to counteract the shadowmap depth precision.

Fix T68380 Skin modifier root not displayed

Fix T70543 Rigid Body Collision Shape Not Displayed In Viewport

Cleanup: Fix wrong assert introduced by rBd98ae27f02c7

Fix T70644 EEVEE: Bump issue with geometry node normal coordinate

Was caused by non-normalized coordinates (normals). Note this is not 100%
correct as the dFdx functions can be the same for packs of 4 pixels and the
derivated value can only be correct for one pixels.

This is because smoothed normals are a non-linear function (because of the
normalization).

The correct fix would be to do the dFdx offset BEFORE any normalization.

Fix T70614 EEVEE: Bump with texture connected to other branches don't work

Was caused by the bump node not being evaluated because the other branch
was evaluated before.

To fix this, we use fromnode instead of tonode.

Also we fix a potential issue with recursiveness because
ntree_shader_copy_branch() also use nodeChainIterBackwards() which would
reset the iter_flag in the middle of the parent iteration. Use iter_flag
as a bitflag for each iteration to fix this.

Fix T70659 Warning, Regression, slow vertex selection

This changes the fix for T70302 by reducing the number of things we discard.