The asset handle type is supposed to be replaced by the asset
representation type. It is designed for the asset system as opposed to
the file browser backend. With d421ebac5e, d04cd3f3e6 and f6a6b27ac1, it
can now do everything that is needed in Python to be a replacement.
With this commit the asset handle type and the file handle type it uses
is almost entirely replaced in Python files (only for the asset view
template we require a collection property taking asset handles still,
for internal reasons.)
Part of #102877 and #108806.
Julian Eisel
591a1ae323