`current_working_directory` may read out of bounds and uninitialized memory with long paths

[BurningEnlightenment]

https://github.com/ned14/llfio/blob/ee65f1b99ecdf12ee0d011e3d8e3b1c6eae67644/include/llfio/v2.0/detail/impl/windows/path_discovery.ipp#L162-L168

GetCurrentDirectory returns the required buffer size if the path doesn't fit into the given buffer (see Windows docs). In case of a long path aware application this can lead to passing the uninitialized buffer with an out of bounds size to the fs_handle constructor.

[BurningEnlightenment]

@ned14 given that we generally don't allocate heap memory, we would either need to increase the buffer size to 2^15 or check written > MAX_PATH and return an error code, right?

[ned14]

Sorry, forgot about this one with the Varna meeting. And I'm heading to New York tomorrow for a few days for the new job.

Stack is cheap on Windows, so I'd just bump that buffer to 32769 like most other parts of LLFIO.

[BurningEnlightenment]

Fixed by fed9ca7c7323ad9dc1cee97bc12c6e0aea28d28a