Fix dirent struct copy causing EXC_BAD_ACCESS in FileSystemService

[sentry]

This PR addresses an EXC_BAD_ACCESS crash occurring in FileSystemService.listDirectoryWithIgnoreDetection.

Root Cause:
The readdir system call can return a pointer to a dirent record that is located near the end of a memory page. The original code copied the entire dirent struct (which is over 1024 bytes) by value using direntPtr.pointee. When the record was near a page boundary, this copy operation would attempt to read past the end of the mapped memory page into unmapped memory, triggering a KERN_INVALID_ADDRESS page fault.

Solution:
To prevent the full struct copy, the decodeDirentName function has been refactored to accept an UnsafePointer<dirent> instead of a dirent value. Inside decodeDirentName, UnsafeRawPointer and byte offsets are now used to read only the necessary fields (d_namlen, d_reclen, d_type, and d_name) directly from the pointer, avoiding any large memory copy that could cross a page boundary. The DecodedDirentName struct was updated to include dType.

Additionally, fileTypeFallback and descriptorRelativeMode functions, which also accepted dirent by value, have been updated to accept UnsafePointer<dirent> and read d_name bytes via raw pointer offsets. All call sites for these functions have been updated to pass the UnsafePointer<dirent> directly, eliminating the problematic .pointee dereference.

Fixes REPOPROMPT-A9