Fix TypeError in MultiplexedPath.joinpath calls

[tomvdw]

Fix TypeError in MultiplexedPath.joinpath calls

Change path.joinpath(*multiple_args) to iterative .joinpath() calls.
In newer Python versions, epath.resource_path returns an
importlib.resources.readers.MultiplexedPath whose joinpath method only
accepts a single positional argument in some execution environments (or via
certain compatibility patches). Unpacking multiple path components into it
results in a TypeError.

Iteratively calling .joinpath resolves the error and remains fully
compatible with standard pathlib.Path objects.

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PR created automatically by Jules for task 16329133361061968178 started by @tomvdw

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