Add support of SAI warm boot testing

[zikkend]

Summary

Add warm boot testing support by extending Sai and SaiClient API

How to run new test

Build Docker image for SAI Redis client:

./build.sh -a trident2 -t saivs 
./run.sh -a trident2 -t saivs

Run test:

./exec.sh -t saivs pytest --testbed=saivs_standalone -v test_warm_reboot.py

Test results

===================================================================== test session starts ======================================================================
platform linux -- Python 3.11.2, pytest-9.1.1, pluggy-1.6.0 -- /usr/bin/python3
cachedir: .pytest_cache
metadata: {'Python': '3.11.2', 'Platform': 'Linux-6.17.0-35-generic-x86_64-with-glibc2.36', 'Packages': {'pytest': '9.1.1', 'pluggy': '1.6.0'}, 'Plugins': {'metadata': '3.1.1', 'html': '4.2.0', 'dependency': '0.6.1'}}
rootdir: /sai-challenger/tests
configfile: pytest.ini
plugins: metadata-3.1.1, html-4.2.0, dependency-0.6.1
collected 2 items                                                                                                                                              

test_warm_reboot.py::test_warmboot PASSED                                                                                                                [ 50%]
test_warm_reboot.py::test_two_warmboots PASSED                                                                                                           [100%]

====================================================================== 2 passed in 34.51s ======================================================================