Related to #1

Adds a new method vfs_get_file_size() to directly retrieve the size of a file in the VFS subsystem. This method enhances the accessibility of file size information, making it more efficient to obtain this data without navigating through file metadata structures.

• Implements vfs_get_file_size() in fs/read_write.c, which returns the size of a file by reading the i_size attribute from the file's inode.
• Exports the symbol vfs_get_file_size to make it accessible for use in other parts of the kernel.
• Ensures error handling for invalid file descriptors or when the inode is not available, returning appropriate error codes in such cases.

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