xcodedeps: provide package root dir (#11818)
xcodedeps: provide package root dir (#11818)

If one wants to access other folders than the provided ones (like
resources), the provided variables dont contain enough information
to access these folders.

Provide a new variable, `PACKAGE_ROOT_<package>` pointing
to the root directory of the package allowing to use it within xcode.

We have to pass the package folder as another parameter, because the
`transitive_cpp_info` variable does not contain the `rootpath`
attribute and we also cant access the package_folder attribute from
`self._conanfile.dependencies.package_folder` directly because
the package name is already formatted via `_format_name`.
conan-io/conan,conan-io/conan,conan-io/conan