Merge branch 'blender-v2.93-release'

RigidBodies: Clarify usage of the custom density in the calculate mass
operator

This is only used when the preset is set to 'Custom', make that clear in
the tooltip and disable editing the value if another preset is used.

Issue came up in T88155.

Maniphest Tasks: T88155

Differential Revision: https://developer.blender.org/D11210

Merge branch 'blender-v2.93-release'

Fix T88188: Keyframing Vertex Mass in Cloth Simulation doesn't have any
effect

The way it is now, `ClothVertex->mass` is setup once for the clothObject
and then reused if it already exists [so does not change across frames/
steps] which happens in`cloth_from_object` / `do_init_cloth`, where
`SIM_cloth_solver_init` / `SIM_mass_spring_set_vertex_mass` are called
and set up masses in `Implicit_Data`.

Seems possible to update `ClothVertex->mass` every step in
`do_step_cloth`, however it seems more involved to update the masses in
`Implicit_Data` there as well. The masses from `Implicit_Data` are
accessed in many places, so it would be mandatory to have these masses
kept up-to-date (and even then it is unclear if the solver was designed
to work with these animated or if there are assumptions about this being
stable across the sim).

So propose to remove the (broken/not implemented) animation capabilities
on the property instead.

Maniphest Tasks: T88188

Differential Revision: https://developer.blender.org/D11225

Merge branch 'blender-v2.93-release'

Fix T87715: Eevee: Holdout options not available in Outliner Collection context menu

Collection holdouts are now supported by eevee.

Maniphest Tasks: T87715

Differential Revision: https://developer.blender.org/D11233

Merge branch 'blender-v2.93-release'

Fix T88234: Crash with Eevee when shader displacement socket connection is muted

In {rB266cd7bb82ce}, support for muting links was added. It might be
debatable if we define a shader as "having" displacement even if the link
is muted, but after said commit, shader_has_displacement() would return
true but still leave the returned node as NULL.

Now also return false if the link is muted (otherwise the caller would
need to additionally check the returned node as well.)

Maniphest Tasks: T88234

Differential Revision: https://developer.blender.org/D11256

Merge branch 'blender-v2.93-release'

Conflicts:
source/blender/editors/object/object_add.c

GPencil: fix separate points/strokes freezing with empty selection

Code would still create an object (without setting up materials), code
for removing unused material slots would then freeze.

Now return/cancel early in case of empty selection.

This came up in T88269 [which is still not fully fixed, transforming
curve edit points clear their GP_STROKE_SELECT flag which now results in
the early exit, should be looked at separately]

Maniphest Tasks: T88269

Differential Revision: https://developer.blender.org/D11252