## Description
This change introduces a new canonicalization pattern for the MLIR
Vector dialect that optimizes chains of insertions. The optimization
identifies when a vector is **completely** initialized through a series
of vector.insert operations and replaces the entire chain with a
single `vector.from_elements` operation.
Please be aware that the new pattern **doesn't** work for poison vectors
where only **some** elements are set, as MLIR doesn't support partial
poison vectors for now.
**New Pattern: InsertChainFullyInitialized**
* Detects chains of vector.insert operations.
* Validates that all insertions are at static positions, and all
intermediate insertions have only one use.
* Ensures the entire vector is **completely** initialized.
* Replaces the entire chain with a
single vector.from_elementts operation.
**Refactored Helper Function**
* Extracted `calculateInsertPosition` from
`foldDenseElementsAttrDestInsertOp` to avoid code duplication.
## Example
```
// Before:
%v1 = vector.insert %c10, %v0[0] : i64 into vector<2xi64>
%v2 = vector.insert %c20, %v1[1] : i64 into vector<2xi64>
// After:
%v2 = vector.from_elements %c10, %c20 : vector<2xi64>
```
It also works for multidimensional vectors.
```
// Before:
%v1 = vector.insert %cv0, %v0[0] : vector<3xi64> into vector<2x3xi64>
%v2 = vector.insert %cv1, %v1[1] : vector<3xi64> into vector<2x3xi64>
// After:
%0:3 = vector.to_elements %arg1 : vector<3xi64>
%1:3 = vector.to_elements %arg2 : vector<3xi64>
%v2 = vector.from_elements %0#0, %0#1, %0#2, %1#0, %1#1, %1#2 : vector<2x3xi64>
```
---------
Co-authored-by: Yang Bai <yangb@nvidia.com>
Co-authored-by: Andrzej Warzyński <andrzej.warzynski@gmail.com>
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