[cleaner] periodic cleanup of mapping files.

[TrevorBenson]

_Originally posted by @NikhilKakade-1 in: #3097 (comment)

https://github.com/sosreport/sos/blob/main/sos/cleaner/parsers/__init__.py#L97

The time complexity of the provided function becomes:

Worst Case: O(k * n * m)
Best Case: O(k * m)

In my opinion, optimizing the data masking process is essential. In terms of computational complexity, the worst-case scenario is O(k * n * m), where k is the number of lines, n is the number of compiled regexes in self.mapping.compiled_regexes, and m is the average length of the lines. Conversely, the best case is O(k * m).

I've been mulling over a few questions.

1. Should we consider period>\ic cleanup of mapping files as the number of compiled regexes increases over time, potentially impacting total processing time?

Yes, it is worth raising a separate issue for the periodic cleanup of mapping files.

Originally posted by @pmoravec in #3097 (comment)

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My response was if automating a removal of map regexes for obfuscation it seemed that tracking the temperature (ie.e most recent time a regex map obfuscation was used) may be required. I also thought that it should be left to the user when to enable this removal of past regex maps. However, a consistent hash and stored salt mentioned by @pmoravec might make the automated cleanup less of a concern. At least if I followed everything properly the regex map for the same sensitive data being created would likely result in the same obfuscation map entry, given the same hash method and stored salt.