[mlir][sparse] Avoid values buffer reallocation for annotated all dense tensors.

Previously, we rely on the InsertOp to gradually increase the size of the
storage for all sparse tensors. We now allocate the full size values buffer
for annotated all dense tensors when we first allocate the tensor. This avoids
the cost of gradually increasing the buffer and allows accessing the values
buffer as if it were a dense tensor.

Reviewed By: Peiming

Differential Revision: https://reviews.llvm.org/D141516