🔨 💥 Separate binary from shell

Separate the binary from the Shell

The two boxed callbacks only reserve 32 bytes on the stack, versus the 120 for the liner context, so hopefully this means faster execution in non-interactive mode, and an only a minor, unnoticeable, change in performance for interactive sessions. Furthermore, I felt like the binary part was a separate concern from the main shell instance. This is a good step toward Ion acting as an independent library.

Breaking changes:

• set does not control interactive session parameters anymore (the current replacement is with shell parameters, maybe a custom command is more fit)
• history now does not exist in non-interactive sessions