[MLIR] Adopt `DenseI64ArrayAttr` in tensor, memref and linalg transform

This commit is a first step toward removing inconsistencies between dynamic
and static attributes (i64 v. index) by dropping `I64ArrayAttr` and
using `DenseI64ArrayAttr` in Tensor, Memref and Linalg Transform ops.
In Linalg Transform ops only `TileToScfForOp` and `TileOp` have been updated.

See related discussion: https://discourse.llvm.org/t/rfc-inconsistency-between-dynamic-and-static-attributes-i64-v-index/66612/1

Reviewed By: nicolasvasilache

Differential Revision: https://reviews.llvm.org/D138567