Refactor ConfiginfoBuilder: Enforce JSON-only configuration, remove defaults, enforce factory pattern (#159)

* Initial plan

* Implement ConfiginfoBuilder refactoring: add JSON config loading, update defaults, make constructor private

Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

* Add tests for JSON configuration file loading functionality

Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

* Add JSON configuration example and update documentation

Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

* Address code review: improve exception handling with specific catch blocks

Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

* Address reviewer feedback: remove default values, add parameterless Create() method

- Removed default values from DefaultBlackFormats (now empty array)
- Removed default values from _mainAppName, _clientVersion, _upgradeClientVersion, _appSecretKey, _productId
- Added parameterless Create() method that loads from update_config.json only
- Kept parameterized Create(url, token, scheme) for programmatic configuration
- Updated all tests to set required fields explicitly
- Updated example code to demonstrate JSON-based configuration

All 39 tests pass.

Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

* Remove parameterized Create() method - JSON config file only

- Removed Create(url, token, scheme) overload per reviewer feedback
- Only parameterless Create() method remains, which loads exclusively from update_config.json
- Updated all tests to create JSON config files instead of using parameterized Create
- Added helper methods CreateTestConfigFile() and CleanupTestConfigFile() for tests
- All 37 ConfiginfoBuilder tests passing

Configuration must now be done through JSON file - highest priority per requirements.

Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: JusterZhu <11714536+JusterZhu@users.noreply.github.com>

Author: Copilot