Listing the "Blender Foundation" as copyright holder implied the Blender
Foundation holds copyright to files which may include work from many
developers.
While keeping copyright on headers makes sense for isolated libraries,
Blender's own code may be refactored or moved between files in a way
that makes the per file copyright holders less meaningful.
Copyright references to the "Blender Foundation" have been replaced with
"Blender Authors", with the exception of `./extern/` since these this
contains libraries which are more isolated, any changed to license
headers there can be handled on a case-by-case basis.
Some directories in `./intern/` have also been excluded:
- `./intern/cycles/` it's own `AUTHORS` file is planned.
- `./intern/opensubdiv/`.
An "AUTHORS" file has been added, using the chromium projects authors
file as a template.
Design task: #110784
Ref !110783.
Introduce a context manager that temporarily overrides a UILayout's
operator context.
Instead of writing this:
```py
default_op_context = layout.context
layout.context = 'OTHER_VALUE'
layout.do_stuff()
layout.context = default_op_context
```
you can now write this:
```py
from bl_ui_utils.layout import operator_context
with operator_context(layout, 'OTHER_VALUE'):
layout.do_stuff()
```
This is also exception-safe; it will always ensure the layout's operator
context is restored when the `with` body is exited, regardless of
whether that's done with an exception or regularly.
Idea in-the-hallway approved by @Sergey.
