[MLIR][Affine] NFC: Move AffineValueMap and MutableAffineMap

Summary:
The `AffineValueMap` is moved into `Dialect/AffineOps` to prevent a cyclic
dependency between `Analysis` and `Dialect/AffineOps`.

Reviewers: bondhugula, herhut, nicolasvasilache, rriddle, mehdi_amini

Reviewed By: rriddle, mehdi_amini

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74277