Describes notification rule watch scope.
Since TC 10 there are 2 types of WatchedBuilds: SYSTEM_WIDE and SPECIFIC_PROJECT_BUILD_TYPES (see WatchType).
SYSTEM_WIDE stands for non-builds related events like investigations, tests and so on.
SPECIFIC_PROJECT_BUILD_TYPES stands for build related events and could be filtered by projects and build configurations.
In case there are no projects and build configurations watched WatchedBuilds will cover all projects (same as watched _Root)