Merge branch 'chore/MSP-11615/update-db-schema' into chore/MSP-11614/remove-msf-db-manager-sink

MSP-11614
Remove Msf::DBManager::Sink

MSP-11614

`Msf::DBManager::Sink` contains code for a `sink` that is a meant to
serialize database events, but it's unneeded because all database events
go directly through ActiveRecord, which handles threading.
Remove Msf::TaskManager

MSP-11614

`Msf::TaskManager` was only used for `Msf::DBManager#sink`, which was
removed because it was unused, so `Msf::TaskManager` can also be
removed.
Merge branch 'master' into chore/MSP-11614/remove-msf-db-manager-sink

MSP-11614

Conflicts:
	spec/lib/msf/core/task_manager_spec.rb
Merge branch 'landing/4205' into upstream-master

Land #4205

* Remove unused Msf::DBManager::Sink
* Part of improvements to thread management