Cleanup: clang-format

Cycles: Add command line option for overriding the compute device

The current way of setting the compute device makes sense for local
use, but for headless rendering it it a massive pain to get Cycles
to use the correct device, usually involving entire Python scripts.

Therefore, this patch adds a simple command-line option to Blender
for specifying the type of device that should be used. If the option
is present, the settings in the user preferences and the scene are
ignored, and instead all devices matching the specified type are used.

Differential Revision: https://developer.blender.org/D9086

Merge branch 'blender-v2.90-release'

Fix T77298: Can't bake texture with multiple objects

The problem here is that the baking code uses tiles to exchange pixel data with
the renderer since a recent-ish refactor, but the code that sent data to the
renderer did not initialize the bake result pixels.

Therefore, when the baking process for the second object started, Cycles
received empty tiles and sent them back as-is if the second object did not
cover them.

By initializing the tiles with the result of the previous bakes, we avoid this
problem.

Fix unreported crash in gpu_free_unused_buffers

As far as I can see, this problem was introduced with the gpu_free_unused_buffers() changes in rB97b597c.

The code checks the returned pointer to stop looping, but the last iteration will return the last GPUTexture and set the queue to NULL, meaning that the next pop() will crash.

Differential Revision: https://developer.blender.org/D8468

Cycles: Add control for sun intensity in Sky Texture and change altitude to km

Differential Revision: https://developer.blender.org/D8091

Cycles: Change precomputed Sky Texture mapping to prioritize the horizon

Differential Revision: https://developer.blender.org/D8091

Cycles: Account for Sky Texture mapping in the sun sampling code

Differential Revision: https://developer.blender.org/D8091

Cycles: Clamp Sky Texture altitude to avoid numerical issues

Differential Revision: https://developer.blender.org/D8091

Sky: Code style and formatting fixes

Differential Revision: https://developer.blender.org/D8091