Fix#3124Fix#3004
Instead of loading a set 7 days of history. Better performance when there are lots of messages, and better context when friends haven't talked in over a week.
Removed historyBaselineDate, introduced in deb8440c6a to fix duplicate messages, but duplicate messages were very likely fixed by https://github.com/qTox/qTox/pull/4607.
Also refactored history loading.
This commit removes historykeeper and code only used by it.
BREAKING CHANGE:
qTox can't open old historykeeper chatlogs after this commit. Use
previous versions to migrate to the new database.
qTox will automatically import the old history on startup.
This new database code is much more robust.
It is very resilient and will not corrupt or disappear after a crash or
power failure, unlike the old code.
The on-disk database format is also much more compact now.
The database sync option in the advanced settings has been removed,
we know run many database operations asynchronously so performance
should not be a problem anymore, but we always ensure resiliency
in case of abrupt termination, so there is no tradeoff anymore.