[OpenVINO Backend] update slice method

[Mohamed-Ashraf273]

Hi @rkazants
I've updated ops.slice to support OpenVINOKerasTensor slicing, which I need for the GSoC project.
Could you please review it?
Thanks!

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 73.68421% with 5 lines in your changes missing coverage. Please review.

Project coverage is 82.72%. Comparing base (771b001) to head (40adae6).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
keras/src/backend/openvino/core.py	73.68%	1 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #21361      +/-   ##
==========================================
+ Coverage   82.70%   82.72%   +0.02%     
==========================================
  Files         565      565              
  Lines       54894    54909      +15     
  Branches     8517     8522       +5     
==========================================
+ Hits        45398    45424      +26     
+ Misses       7415     7398      -17     
- Partials     2081     2087       +6     

Flag	Coverage Δ
keras	82.53% <73.68%> (+0.02%)	⬆️
keras-jax	63.55% <0.00%> (-0.02%)	⬇️
keras-numpy	58.71% <0.00%> (-0.02%)	⬇️
keras-openvino	33.58% <73.68%> (+0.04%)	⬆️
keras-tensorflow	63.94% <0.00%> (-0.02%)	⬇️
keras-torch	63.58% <0.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[rkazants]

@fchollet, looks good to me. Recommend to merge