This is mostly the same as blender/blender!140195. The header parsing code has
been updated to be able to read old and new .blend file headers.
There is a new test file which is the same as the existing `basic_file.blend`,
but saved with the new header format. A new unit test has been added to check
that this file is read correctly as well.
Pull Request: https://projects.blender.org/blender/blender-asset-tracer/pulls/92893
This does introduce some not-so-nice things, like having to annotate each
`__init__` function with `-> None`. However, the benefits of having static
type checking in a complex bit of software like BAT outweigh the downsides.
