Migrate ActionLog data to include is_explicit_action field

[harmitgoswami]

As part of PR #3442 a new boolean ActionLog.is_implicit_action was created.

This field is used to distinguish between actions that are caused directly (incl. by system users like sync) and actions that are a consequence of a previous action (e.g. auto-rejecting an approved string by submitting a new translation for the same entity).

PR #3442 shipped on December 11, 2024 and all ActionLog entries created since then correctly store the value of the is_implicit_action field. We still need to migrate the old ActionLog data, though. This code from the aforementioned PR attempted to detect implicit actions, and may be helpful when migrating.