Canonicalize static alloc followed by memref_cast and std.view

Summary: Rewrite alloc, memref_cast, std.view into allo, std.view by droping memref_cast.

Reviewers: nicolasvasilache

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D72379