Refactored the platform layer

The whole platform layer was just one file until now. Since I did a lot of work on it recently, it grew to over 2400 lines of code. It was super confusing and disorienting. So I decided to refactor it (split it) into 8 files, based on what they handle:

• console.h - saving/restoring terminal state
• control.h - termination signal handling
• file.h - file operations (64bit)
• input_reader.h - handling input (not parsing, that is it’s own file)
• shared_memory.h - shared memory handling for the kitty protocol
• terminal_io.h - writes output to the terminal
• terminal_query.h - querying the terminal for things like graphics capability, etc.
• timing.h - frame timing and sleeps