Added dropout support in ConvLSTMCell.

[hertschuh]

Implemented dropout and recurrent dropout in ConvLSTMCell with the same approach as in Keras 2.

Fixes #20063

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 79.31034% with 6 lines in your changes missing coverage. Please review.

Project coverage is 79.29%. Comparing base (445da52) to head (8c7ef30).

Files	Patch %	Lines
keras/src/layers/rnn/conv_lstm.py	71.42%	5 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #20089      +/-   ##
==========================================
- Coverage   79.30%   79.29%   -0.01%     
==========================================
  Files         501      501              
  Lines       46966    46983      +17     
  Branches     8655     8659       +4     
==========================================
+ Hits        37246    37257      +11     
- Misses       7971     7976       +5     
- Partials     1749     1750       +1     

Flag	Coverage Δ
keras	79.15% <79.31%> (-0.01%)	⬇️
keras-jax	62.48% <79.31%> (+<0.01%)	⬆️
keras-numpy	57.50% <34.48%> (-0.02%)	⬇️
keras-tensorflow	63.83% <79.31%> (+<0.01%)	⬆️
keras-torch	62.52% <79.31%> (+<0.01%)	⬆️

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[fchollet]

LGTM -- thank you for the fix.