[mlir][VectorOps] Adds canonicalization rewrite patterns for vector ShapeCastOp.

Summary:
Adds two rewrite patterns for the vector ShapeCastOp.
*) ShapeCastOp decomposer: decomposes ShapeCastOp on tuple-of-vectors to multiple ShapeCastOps each on vector types.
*) ShapeCastOp folder: folds canceling shape cast ops (e.g. shape_cast A -> B followed by shape_cast B -> A) away.

Reviewers: nicolasvasilache, aartbik

Reviewed By: nicolasvasilache

Subscribers: mehdi_amini, rriddle, jpienaar, burmako, shauheen, antiagainst, arpith-jacob, mgester, lucyrfox, liufengdb, Joonsoo, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74327