[mlir][VectorOps] Implement insert_strided_slice conversion

Summary:
This diff implements the progressive lowering of insert_strided_slice.
Two cases appear:
1. when the source and dest vectors have different ranks, extract the dest
subvector at the proper offset and reduce to case 2.
2. when they have the same rank N:
  a. if the source and dest type are the same, the insertion is trivial:
     just forward the source
  b. otherwise, iterate over all N-1 D subvectors and create an
     extract/insert_strided_slice/insert replacement, reducing the problem
     to vecotrs of the same N-1 rank.

This combines properly with the other conversion patterns to lower all the way to LLVM.

Reviewers: ftynse, rriddle, AlexEichenberger, andydavis1, tetuante, nicolasvasilache

Reviewed By: andydavis1

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D72317

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