Move K/N dependencies handling logic into gradle plugins:
`NativeDependenciesDownloader` is instantiated in
`:kotlin-native:dependencies` and provides a single configuration that
contains all directories with the dependencies. The configuration has
a variant for each target.
`NativeDependencies` is instantiated by projects that require native
dependencies (i.e. previously used to depend on
`:kotlin-native:dependencies:update`). This plugin creates a configuration
that by default depends on `:kotlin-native:dependencies`. Its extension
provides `llvmDependency`, `libffiDependency`, `hostPlatformDependency`,
`targetDependency()` to depend on the parts needed for the project and
provides accessors `llvmPath`, `libffiPath`, `hostPlatform` that are
safe to use during configuration time, but which do not automatically
resolve those dependencies.
`llvmDir`, `*LibffiDir` properties on `:kotlin-native` are removed
completely, as their use is replaced by `NativeDependencies`. As a
consequence, `evaluationDependsOn(":kotlin-native:dependencies")` is
also gone.
All direct dependencies on `:kotlin-native:dependencies:update` are
replaced with dependencies on specific parts via `NativeDependencies`
Alexander Shabalin
4922223bec