update doc and test cases

[liunick-msft]

This pull request focuses on improving documentation clarity and updating test coverage for the network configuration generator tool. The main README has been streamlined to simplify the quick start process, and a new summary of test cases has been added. Additionally, new expected output files have been introduced for Cisco NX-OS "switched" scenarios and Dell OS10 BMC switch convertor tests.

Documentation improvements:

• The README.md quick start section has been simplified by removing redundant subsections and now directs users to a consolidated docs/QUICK_START.md guide. The "Choose Your Path", "Basic Usage", and "Quick Examples" sections were removed in favor of a single link to the new quick start guide, and all references to docs/EXECUTABLE_USAGE.md have been updated to docs/QUICK_START.md. [1] [2] [3] [4]
• The new docs/QUICK_START.md (renamed from docs/EXECUTABLE_USAGE.md) now provides a concise overview of command-line usage, available options, and examples, including a demo GIF. Redundant or overly detailed sections have been removed or condensed. [1] [2]

Test coverage and expected outputs:

• Added tests/TEST_CASES_SUMMARY.md, which provides a clear summary of test coverage, pass/fail/skip status, and a breakdown of test scenarios for both the configuration generator and lab input convertor.
• Added a new expected output file for Dell OS10 BMC switch convertor tests: tests/test_cases/convert_lab_switch_input_json_dell_os10/expected_outputs/s46-r06-3248bmc-6-1.json.
• Added new expected configuration output files for the "std_cisco_nxos_switched" scenario, including BGP, interface, login, port channel, prefix list, QoS, and system configuration files. [1] [2] [3] [4] [5] [6] [7]