Move file collection APIs out of core (#6525) This change breaks out code that directly relates to handling `FileCollection`s and their build dependencies (called `TaskDependency` at this time) into a separate subproject (`:files`). This is so that other modules can build on just this module instead of having to depend on the oversized `:core`.
As part of the change `Provider`s have been moved to `:base-services`. In a possible followup step `:base-services` could be split into a module that captures the very basic concepts of Gradle's data model: it's all about `DomainObjectCollection`s that can be configured via `Action`s, transformed via `Transformer`s, lazyness can be provided via `Provider`s and rich mutable data types can be created via `Property` objects.
Another addition to `:base-serivces` is the directed graph traversal algorithms used in many parts of Gradle.