Refactor incremental stats framework

[amCap1712]

Separate IncrementalStats class into Selector, Provider, MessageCreator and Aggregator. Builds on #3114, #3115, #3116.

[pep8speaks]

Hello @amCap1712! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file listenbrainz_spark/stats/incremental/user/listening_activity.py:

Line 97:74: W292 no newline at end of file

• In the file listenbrainz_spark/stats/user/tests/test_listening_activity.py:

Line 112:131: E501 line too long (133 > 130 characters)
Line 114:131: E501 line too long (133 > 130 characters)
Line 116:131: E501 line too long (133 > 130 characters)
Line 118:131: E501 line too long (133 > 130 characters)
Line 131:131: E501 line too long (135 > 130 characters)
Line 133:131: E501 line too long (135 > 130 characters)

Comment last updated at 2025-01-26 16:23:03 UTC

[amCap1712]

This refactor is necessary for re-using code with the popularity data generation.