[FSSDK-11463] C# - Add SDK Multi-Region Support for Data Hosting

[esrakartalOpt]

Summary

• Add Multi-Region Support for Data Hosting

Test plan

• Created and added new test cases

Issues

• FSSDK-11463

[Copilot]

Pull Request Overview

This PR adds multi-region support for data hosting in the Optimizely C# SDK, allowing event dispatching to region-specific endpoints (US and EU) rather than hardcoding the US endpoint.

Key changes:

• Added Region property to ProjectConfig interface and implementation
• Replaced hardcoded US event endpoint with configurable region-specific endpoints
• Updated event factories to use region-based endpoint selection with US as fallback

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
OptimizelySDK/ProjectConfig.cs	Added Region property to ProjectConfig interface
OptimizelySDK/Config/DatafileProjectConfig.cs	Implemented Region property and cleaned up string formatting
OptimizelySDK/Event/EventFactory.cs	Added region-specific endpoint mapping and selection logic
OptimizelySDK/Event/Entity/EventContext.cs	Added Region property to EventContext with builder pattern support
OptimizelySDK/Event/UserEventFactory.cs	Updated to include region in event context creation
OptimizelySDK/Event/Builder/EventBuilder.cs	Updated deprecated builder to use new region-aware endpoints
OptimizelySDK.Tests/OptimizelyTest.cs	Updated test to use new endpoint reference
OptimizelySDK.Tests/EventTests/TestForwardingEventDispatcher.cs	Updated test assertion to use new endpoint reference
OptimizelySDK.Tests/EventTests/EventFactoryTest.cs	Added comprehensive tests for EU and invalid region handling, updated existing tests
OptimizelySDK.Tests/EventTests/EventBuilderTest.cs	Updated all test assertions to use new endpoint references

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