fixup! [mlir][linalg][nfc] Move vectorization tests

* In vectorize-convolution.mlir, switch from
  `-test-linalg-transform-patterns=test-linalg-to-vector-patterns` to
  `transform.structured.vectorize_children_and_apply_patterns` (for
  consistency with other tests for vectorization).
* Move + rename the remaining vectorization tests.
* Add comments.

Author: banach-space

mlir/test/Dialect/Linalg/vectorize-convolution-flatten.mlir renamed to mlir/test/Dialect/Linalg/vectorization/convolution-with-patterns-flatten.mlir

@@ -1,5 +1,11 @@
 // RUN: mlir-opt -split-input-file -transform-interpreter %s | FileCheck %s
 
+///----------------------------------------------------------------------------------------
+/// Tests for vectorizing depthwise convolutions (with patterns) with the
+/// flattening of the channel dim enabled. This approach is beneficial when the
+/// number of channel dimensions is low.
+///----------------------------------------------------------------------------------------
+
 func.func @depthwise_conv1d_nwc_wc_1x8x3xi8_tensor(%input: tensor<1x8x3xi8>,
                                                    %filter: tensor<1x3xi8>,
                                                    %output: tensor<1x8x3xi8>) -> (tensor<1x8x3xi8>) {