perf: Use enum types for compression and encoding instead of strings

[luoluoyuyu]

• Change compression type fields from String to CompressionType enum
• Change encoding type fields from String to TSEncoding enum
• Optimize getCompressor() method to use direct field access instead of string conversion
• Optimize getValueEncoder() to return TSEncoding directly instead of String
• Update all callers to remove unnecessary TSEncoding.valueOf() conversions
• Improve performance by avoiding string conversions in hot paths