Previously cache_dir was located under site-packages, which is managed
by blender and could be read-only. Now location defaults to eg.
~/.cache/bonsai or equivalent location on other platforms. See #5564
Note this adds a dependency on the platformdirs python module
Previously it would fail with:
PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: 'bonsai\\bim\\data\\cache\\988c190483ae6bab7cf6b00cee78694d.h5'
Dion Moult
