[ENH] Avoid hidden modification of variables within find_sub_ses_pattern_path / remove Parallel processing

[AliceJoubert]

As noticed in PR #1285, the function find_sub_ses_pattern_path (renamed as find_images_path) from utils/inputs.py currently returns nothing because it modifies its input :

clinica/clinica/utils/inputs.py

Lines 273 to 281 in 954d4a9

	def find_sub_ses_pattern_path(
	input_directory: os.PathLike,
	subject: str,
	session: str,
	error_encountered: list,
	results: list,
	is_bids: bool,
	pattern: str,
	) -> None:

The lists results and error_encountered are incremented within the function. It would be better to have it copy the input and return the modified version of the copy rather than modifying the input sneakily.

This function is only used twice, including in a Parallel processing :

clinica/clinica/utils/inputs.py

Lines 778 to 792 in 954d4a9

	manager = Manager()
	shared_results = manager.list()
	shared_errors_encountered = manager.list()
	Parallel(n_jobs=n_procs)(
	delayed(find_sub_ses_pattern_path)(
	input_directory,
	sub,
	ses,
	shared_errors_encountered,
	shared_results,
	is_bids,
	pattern,
	)
	for sub, ses in zip(subjects, sessions)
	)

That Parallel processing may not be efficient for the task it is used for, and could be replaced (to investigate).

[github-actions]

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