[mlir][VectorToLLVM] Fix crash in VectorInsertOpConversion with dynamic index (#183783)
VectorInsertOpConversion crashes with an assertion failure when
inserting a sub-vector at a dynamic position into a multi-dimensional
vector. The pattern calls getAsIntegers() on the position, which asserts
that all fold results are compile-time constant attributes.
The existing guard (checking llvm::IsaPred<Attribute>) only covered the
case where a scalar is inserted into the innermost dimension (the
extractvalue path). The guard was missing for the insertvalue path when
inserting a sub-vector at a dynamic position into a nested aggregate.
Fix: add the same guard before the llvm.insertvalue creation to return
failure() gracefully when any position index is dynamic, matching the
behavior of VectorExtractOpConversion.
Fixes #177829