Asset library indexing would store indexes of asset files to speed up
asset library browsing.
* Indexes are read when they are up to date
** Index should exist
** Index last modify data should be later than the file it indexes
** Index version should match
* The index of a file containing no assets can be load without opening
the index file. The size of the file should be below a 32 bytes.
* Indexes are stored on a persistent cache folder.
* Unused index files are automatically removed.
The structure of the index files contains all data needed for browsing assets:
```
{
"version": <file version number>,
"entries": [{
"name": "<asset name>",
"catalog_id": "<catalog_id>",
"catalog_name": "<catalog_name>",
"description": "<description>",
"author": "<author>",
"tags": ["<tag>"]
}]
}
```
Reviewed By: sybren, Severin
Maniphest Tasks: T91406
Differential Revision: https://developer.blender.org/D12693
