Move to platformdirs instead of deprecated appdirs

[ameraner]

The package appdirs is officially deprecated and not maintained anymore. We should therefore switch to the maintained fork platformdirs: https://github.com/platformdirs/platformdirs .

Appdirs is currently used in e.g.

sift/uwsift/util/default_paths.py

Lines 19 to 27 in ac7d431

	import appdirs
	APPLICATION_AUTHOR = False # used only in Windows, passing False avoids an unnecessary extra parent folder
	APPLICATION_NAME = "SIFT"
	USER_CACHE_DIR = appdirs.user_cache_dir(APPLICATION_NAME, APPLICATION_AUTHOR)
	# Data and config are the same on everything except linux
	USER_DATA_DIR = appdirs.user_data_dir(APPLICATION_NAME, APPLICATION_AUTHOR, roaming=True)
	USER_CONFIG_DIR = appdirs.user_config_dir(APPLICATION_NAME, APPLICATION_AUTHOR, roaming=True)

Note: this issue is ported from the EUM Gitlab issue 200.