implement transform_bounding_boxes for random_zoom

[shashaka]

I have implemented the transform_bounding_boxes method to support random zoom functionality. If this implementation is satisfactory, I can proceed with adding corresponding test cases.

here is gist

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 89.58333% with 5 lines in your changes missing coverage. Please review.

Project coverage is 82.14%. Comparing base (c802ca6) to head (009ef4c).
Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
...s/preprocessing/image_preprocessing/random_zoom.py	89.58%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #20526      +/-   ##
==========================================
+ Coverage   82.10%   82.14%   +0.04%     
==========================================
  Files         515      515              
  Lines       47790    47854      +64     
  Branches     7486     7493       +7     
==========================================
+ Hits        39238    39312      +74     
+ Misses       6738     6730       -8     
+ Partials     1814     1812       -2     

Flag	Coverage Δ
keras	81.99% <87.50%> (+0.04%)	⬆️
keras-jax	65.10% <83.33%> (+0.05%)	⬆️
keras-numpy	60.08% <83.33%> (+0.05%)	⬆️
keras-tensorflow	66.08% <83.33%> (+0.04%)	⬆️
keras-torch	65.02% <83.33%> (+0.05%)	⬆️

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[fchollet]

The code looks great! Please add a unit test.

[shashaka]

I've added test cases. If there are any corrections needed, please feel free to share them with me.

[fchollet]

Thanks for the update! The tests are looking good.

[fchollet]

Please move the functions _get_transformed_x_y and _get_clipped_bbox to be methods on the layer class rather than inlined function (for better eager performance).

[shashaka]

I have moved these functions to layer class. Thank you for your guidance.

[fchollet]

LGTM, thank you!