CU-869574kvp update snomed preprocessing naming

[mart-r]

As per #467

Using a regular expression to capture the release from the folder name.

Upon init, this check is non-strict (i.e no exception is raised if release is unable to be found) since it could refer to a parent folder.

When parsing through the subfolder, the check is string (i.e an exception is raised if no release is found) since those are expected to be Snomed release folders (with SnomedCT in the names).

Added some relevant tests for working and failing folder names. Both just the base names as well as longer paths. For both strict and non-strict mode.

[tomolopolis]

Task linked: CU-869574kvp Improve Snomed preprocessing folder detection

[mart-r]

This might need some additions:

• We may want to do the release calculations (_check_path_and_release) at init to allow failing early in case it's an incorrect / unknown Snomed release
• It might be useful to automatically detect the UK / UK_drug / AU extension types per sub-folder so as to allow preprocessing all at once

[mart-r]

PS: Reworked the PR. Would need a new review.