Fix dimension order of MVBS dataset

[leewujung]

This PR:

• fixes dimension order of MVBS dataset
  • should be (channel, depth, ping_time), but was (channel, ping_time, depth)
• fixes torch warning by using tensor.clone() for instantiating a copy

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 40.39%. Comparing base (32d2ff4) to head (a7881fe).

Files	Patch %	Lines
echodataflow/stages/subflows/mask_prediction.py	0.00%	4 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## realtime #122 +/- ## ========================================= Coverage 40.39% 40.39% ========================================= Files 41 41 Lines 3050 3050 ========================================= Hits 1232 1232 Misses 1818 1818 ```

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