Use kotlin flatbuffers

[ImUrX]

This comes with many things.

• Better typings, everything that in our schema is an unsigned will be seen like that instead of just being an int.
• Null-safety, nullables are specified now, so we can know if we are getting something that can be null or not.
• Removal of object API aka the .pack() and .unpack() are gonna go
• Flatbuffer creation has some nice things with vectors because they use primitive arrays that come with the kotlin std (nice, no boxing)
• I'm working on adding more type-safety on the offsets so we can have even safer table creation now that there is no object API