Covalence Formatter Performance improvements (#104)

Removed LINQ

Cache translation dictionaries and related Tags

Implement object pooling for Formatter components

- Add `Poolable<T>` base class
- Refactor `Element`, `Token`, `Lexer`, and `Entry` classes to use object pooling
- Add `ElementTreeBuilder` for more efficient element processing
- Refactor parsing workflow to use pooled objects
- Maintain backward compatibility with existing public API

Convert `Lexer` to use enum-based state machine

- Replace delegate-based state machine with enum-based approach
- Reduce memory allocations and improve performance
- Simplify state transitions with direct state assignment

Optimize `ToTreeFormat` with `StringBuilder` pooling

Author: ThePaperPlate