Add ability to follow symlinks during recursive directory traversal

[newhoggy]

This PR introduces the following changes:

• Symlink Traversal Option Adds a SymlinkBehavior option to recursive directory traversal, allowing users to choose whether to follow symlinks to directories. This makes globbing more robust and configurable, addressing portability and correctness concerns. This is not supported on Windows.
• Internal Refactor Moves the optimized doesDirectoryExistFast function to a new System.FilePath.Glob.Internal module for better encapsulation and maintainability.
• API Clarification Renames the optimized directory existence check from doesDirectoryExist to doesDirectoryExistFast to avoid confusion and clarify its purpose.
• Additional changes Comprehensive tests have been added to ensure that both symlink behaviors produce identical results when no symlinks are present.
• Documentation updated to clarify the new behavior and options.

This PR is needed to merge haskell-works/tasty-discover#64 on https://github.com/haskell-works/tasty-discover to resolve haskell-works/tasty-discover#38

This PR also resolve #48