Add a CDN support

[Cinkafox]

Add CDN-based mechanism to identify the fastest available endpoint and implement corresponding routing logic.

UI may change later.

Mechanism Overview

The system operates by substituting all URLs with UriCdnDefinition placeholders. The CDN Manager processes these definitions as follows:

1. Configuration Loading
   A configuration file contains the mapping of UriCdnDefinition entries to their corresponding URLs. On initialization, CdnManager reads this file.

2. Default Values
   If the configuration file is missing or empty, the manager automatically populates it with predefined default values.

3. Performance Optimization
   URLs are sorted by latency (ping) to prioritize the fastest endpoints.

4. Resolution
   The sorted URLs are stored in a dictionary within CdnManager. Clients can resolve a definition to an actual URI using the ResolveDefinition method.