This pull request includes several changes across multiple files to enhance the functionality and performance of the SimpleCDN project. The most important changes focus on adding benchmarking for StringBuilder conversions, simplifying the Redis cache service, and introducing new helper methods.

Benchmarking and Performance Improvements:

• benchmarks/StringBuilderConversionBenchmarks.cs: Added a new benchmarking class StringBuilderConversionBenchmarks to compare the performance of manual and built-in StringBuilder to byte array conversions.
• src/core/Helpers/StringBuilderExtensions.cs: Introduced an extension method ToByteArray for StringBuilder to efficiently convert its contents to a byte array without creating a string copy.

Redis Cache Service Simplification:

• extensions/Redis/CustomRedisCacheService.cs: Simplified the CustomRedisCacheService by removing the ObjectAccessBalancer and directly using a single ConnectionMultiplexer instance. This change also updated methods to handle Redis operations more efficiently.
• extensions/Redis/ObjectAccessBalancer.cs: Removed the ObjectAccessBalancer class as it is no longer needed for managing Redis connections.

Configuration and Logging Enhancements:

• extensions/Redis/RedisCacheConfiguration.cs: Updated the default KeyPrefix to "SimpleCDN::" for better key namespace management in Redis.
• src/core/Services/Caching/Implementations/CacheManager.cs: Changed logging level from LogDebug to LogInformation for cache misses to provide better visibility in logs.

Miscellaneous Improvements:

• src/core/Helpers/InternalExtensions.cs: Reworked the ForLog method to handle ReadOnlySpan<char> more efficiently using a StringBuilder.
• src/core/Services/Caching/Implementations/InMemoryCache.cs: Added a Clear method to the InMemoryCache class for clearing all cached items.

These changes collectively improve the performance, maintainability, and functionality of the SimpleCDN project.