[OpenVINO Backend] support ops.slice_update

[Mohamed-Ashraf273]

Hi @rkazants ,
I've supported ops,silce_update for my GSoC project, but I can't enable tests for it until getting __getitem__ merge.

It could be implemented more easily if we use opset15 instead of opset14.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 42 lines in your changes missing coverage. Please review.

Project coverage is 82.63%. Comparing base (771b001) to head (aef0743).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
keras/src/backend/openvino/core.py	0.00%	42 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #21362      +/-   ##
==========================================
- Coverage   82.70%   82.63%   -0.07%     
==========================================
  Files         565      565              
  Lines       54894    54936      +42     
  Branches     8517     8525       +8     
==========================================
  Hits        45398    45398              
- Misses       7415     7457      +42     
  Partials     2081     2081              

Flag	Coverage Δ
keras	82.44% <0.00%> (-0.07%)	⬇️
keras-jax	63.52% <0.00%> (-0.05%)	⬇️
keras-numpy	58.68% <0.00%> (-0.05%)	⬇️
keras-openvino	33.51% <0.00%> (-0.03%)	⬇️
keras-tensorflow	63.91% <0.00%> (-0.05%)	⬇️
keras-torch	63.55% <0.00%> (-0.05%)	⬇️

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