[Tracking] StructInfo

[tqchen]

• M0: Initial data structure and normalize switch over. [REFACTOR][ARCH] Introduce StructInfo M0 #314
• M1: Change parser/printer to only depend on struct info field, change Var/Function signature to take struct info. [REFACTOR] StructInfo M1: Parser/printer update to focus on StructInfo #319
• M2: Remove shape field, shape() completely, and possible places that pass in RuntimeShape. Change to a ShapeOf(Expr). Remove RuntimeDepShape [REFACTOR] StructInfo M2: Cleanups on legacy shape related items  #320
• M3: Update MatchShape to use MatchCast. [REFACTOR] StructInfo M3: MatchShape=>MatchCast #323