[mlir] [VectorOps] consolidate all vector utilities to one header/cc file

Reviewers: nicolasvasilache, andydavis1, dcaballe

Reviewed By: andydavis1, dcaballe

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D73593