Bug 1933012 [wpt PR 49343] - webnn: Support gatherElements in tflite converter, a=testonly

Automatic update from web-platform-tests
webnn: Support gatherElements in tflite converter

There is no TFLite operator to map directly WebNN gatherElements, but
it can be supported with tfl.gather_nd, the test cases[1] and the
doc[2] show the gather_nd can gether not only slices but also elements,
but gather_nd can't gather along the axis, so the indices used by
gather_nd need to be calculated by unravelling the flat index and
adjusting value with the axis.

The coordinates are calculated by the stride of each dimension. For
example a shape (3, 2) array can map to the following coordinates:
//         index                      row, col
//     [[0,  1,]                  [[0, 0], [0, 1],
//      [2,  3,]      =>            [1, 0], [1, 1]
//      [4,  5,]]                   [2, 0], [2, 1]]

Adjusting the coordinates with WebNN indices operand along the axis,
//   unravelled index   WebNN indices   axis = 0       TFLite indices
//  [[0, 0], [0, 1],     [[1, 0],                  [[1 ,0], [0, 1],
//   [1, 0], [1, 1]       [2, 1],         =>        [2, 0], [1, 1],
//   [2, 0], [2, 1]]      [0, 2]]                   [0, 0], [2, 1]]

[1] https://www.tensorflow.org/mlir/tfl_ops#tflgather_nd_tflgatherndop
[2] https://www.tensorflow.org/guide/tensor_slicing#insert_data_into_tensors

Bug: 40206287
Change-Id: I61ad75585405039da10af05f3300799fe8f32855
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6000111
Reviewed-by: ningxin hu <ningxin.huintel.com>
Reviewed-by: Reilly Grant <reillygchromium.org>
Commit-Queue: Junwei Fu <junwei.fuintel.com>
Cr-Commit-Position: refs/heads/main{#1387213}

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wpt-commits: 038b09dd678084a3fdc828316da9a2f2a03981cf
wpt-pr: 49343

UltraBlame original commit: edbd32557d5a79f628cad8f6f7b2a85003e0f334

Author: marco-c