utils.split_range: Make computed ranges not overlap

Existing listers use the is_within_bound [1] method from the base lister. This method uses inclusive boundaries in all cases.

As some "range" task listers [2] [3] are using split_range function to create "overlapping" ranges, this can be the concurrent insert issue cause we found [4].

This commit adapts the function split_range to make the generated ranges no longer overlap.

• [1] https://forge.softwareheritage.org/source/swh-lister/browse/master/swh/lister/core/lister_base.py$194-199

• [2] https://forge.softwareheritage.org/source/swh-lister/browse/master/swh/lister/gitlab/tasks.py$37-41

• [3] https://forge.softwareheritage.org/source/swh-lister/browse/master/swh/lister/gitea/tasks.py$36-41

• [4] https://sentry.softwareheritage.org/share/issue/aec9c2af347e47ea84f51ace3bfe2f25/

Related to #2577 (closed)

Test Plan

tox

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Migrated from D3899 (view on Phabricator)