Optimize ShouldQuote logic and add write benchmarks

[karpinsn]

Refactored ShouldQuote in ConfigurationFunctions to reduce per-field overhead:

• Check leading/trailing spaces first (cheapest check).
• Fast path: when delimiter is a single char and newline is default, scan the field once instead of making 3-4 separate passes (Contains/IndexOfAny).
• Slow path: fall through to existing multi-char / custom-newline logic.

Added BenchmarkDotNet benchmarks for ShouldQuote and WriteRecords.

Performance results:
ShouldQuote: 1.154 ms -> 0.854 ms (~26% faster)
WriteRecords: 2.427 ms -> 1.808 ms (~25% faster)