Provide a Taggable interface

Provide a Taggable interface

The Taggable interface defines how to tag objects in MediaWiki.
For now there are only two Taggable objects:
 - RecentChange
 - ManualLogEntries

This interface should be used in places where we want to optionally
tag things, for example:
 We want to tag all mobile web actions with 'web mobile edit'.

With that interface, we will be able to expect a Taggable object,
and call `addTags()` when we need to, without having a special check
to verify is it RecentChange, or is it ManualLogEntry. We will only
expect a Taggable object.

Additionally, added @deprecated note to ManualLogEntries::setTags()
as each call to this method will override all previous tags. This
action can be harmfull to parts of code that conditionally add tags.
If object was tagged in some way, we should preserve those tags.

If there are any special cases, where we want to override all tags,
we should provide `resetTags()` method.

Bug: T215675
Change-Id: Ia4c019db8ca6f37ce0f86bf7d134d6f1713daf56