Merge branch 'master' into asset-system-filelist

Mostly finish regular file reading & general improvements

Main thing that's missing for regular file reading is supporting symbolic
links. Most work for them is already done though.

Merge branch 'master' into asset-system-filelist

Merge branch 'master' into asset-system-filelist

Merge remote-tracking branch 'origin/master' into asset-system-filelist

Cleanup: Properly explain TODO marker

Initial framework and basic reading of file-lists

Initial steps for T88184.

Adds a `filelist/` directory to `editors/`, containing C++ classes for
(recursively) reading directories and files into a file-list. The logic is
based on the File-Browser file-list, so that the actually executed logic is
basically the same (avoiding regressions or old issues re-appearing). But it
is entirely re-designed to work for both the asset system and the file browser.

For more info about the design, see T88184.

Also contains "peeking" the file list to count the files to be read. This is to
improve progress reporting later. However, it has some issues and I'm not sure
actually it's something we'll even need in the end, I see other ways to improve
things here.

Merge remote-tracking branch 'origin/master' into asset-browser-poselib

Merge remote-tracking branch 'origin/master' into asset-browser-poselib

Merge remote-tracking branch 'origin/master' into asset-browser-poselib

UI List: Fix segfault in unit tests

Fix `NULL` pointer deference in `ui_list_find_mouse_over()`.

Merge branch 'master' into asset-browser-poselib

Assets: Keep assets active after renaming, ensure they are scrolled into view

See https://developer.blender.org/D11119, just committing this to the branch
for testing already.

Asset: Keep assets active after renaming, make sure they are scrolled into view

I want to clean this up a bit still, but it seems to work now.

Also includes (to be split off):
* Don't allow renaming assets from the file list for now (e.g. right-click >
Rename). This doesn't work yet and I'm not sure it should even. If an asset
is a local data-block it can be renamed in the sidebar.
* Fix broken logic to scroll a preview into view.
* Partially includes D9994. These changes were needed for this to work.

Differential Revision: https://developer.blender.org/D11119

Merge branch 'master' into asset-browser-poselib

Fix incorrect sorting in Asset View after renaming local asset

Basically the same as 88400f0c03a9, but now for the asset view.

Merge branch 'master' into asset-browser-poselib

Merge remote-tracking branch 'origin/master' into asset-browser-poselib

Attempt to fix build error on MSVC and warnings on some other compilers

On MSVC it failed with this error:
```
sourceblenderblenkernelBKE_context.h(361,20): error C2526:
'CTX_wm_asset_handle': C linkage function cannot return C++ class 'AssetHandle'
```

On Apple Clang I would get this:
```
warning: 'CTX_wm_asset_handle' has C-linkage specified, but returns incomplete
type 'struct AssetHandle' which could be incompatible with C
[-Wreturn-type-c-linkage]
struct AssetHandle CTX_wm_asset_handle(const bContext *C, bool *r_is_valid);
^
1 warning generated.
```

Just include the asset header defining the type for now, it should later on be
solved properly with a better design for `AssetHandle`.

UI: Improve walk navigation in UI List template

Add improved arrow key walk navigation in grid layout UI List templates.
Pressing up or down walks the active item to the adjacent row in that
direction, while left and right walk through the items along the columns
wrapping at the rows.

Differential Revision: https://developer.blender.org/D11063