Limit filenames to 255 bytes

[Forty-Bot]

At the moment, we must support filenames of up to 4068 bytes. In addition to not being supported by either Linux or any other major OS, excessively long filenames are both unneccessary and unweildy.

To implement this, the type of lean_dir_entry.name_length would be changed to a uint8_t, and LEAN_DIR_NAME_MAX would be redefined to be 255.

 struct lean_dir_entry {                                                          
        le64 inode;                                                              
        uint8_t type;
        uint8_t entry_length;
        uint8_t name_length;   
        uint8_t name[5];
} __packed;                                                                      
                                                                                 
#define LEAN_DIR_NAME_MAX 255