Forward TBB info through ITKConfig

### Description

For projects that consume ITK through ITKConfig, it is not easy to determine if ITK has been built with TBB support. If tbb support is enabled, that introduces a runtime dependency on the tbb dlls (at least on windows). It would be great if ITKConfig could provide a flag to indicate whether tbb is used, and the appropriate paths to the bin directories.

### Expected behavior

ITKConfig should provide sufficient info for consuming projects.

### Actual behavior

ITKConfig does not provide sufficient info about tbb usage.

### Additional Information

We recently patched for this in [Slicer](https://github.com/Slicer/Slicer/commit/17cdc49fb81da8c0945fa0199c51cf10b67b908a) but it would be nice to have a solution that would work for an ITK built outside of the superbuild.