Add DictType to Metadata (#20770)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20770
Add dict type since it's part of the pytorch built-in system, and sparse features and text features will be converted to Dict
Reviewed By: pritamdamania87
Differential Revision: D15436255
fbshipit-source-id: 239adbd6a8f68be29020fe656d790f6872f1f0e9
