feat(tazjin/rlox): Support trivial literals in bytecode compiler

Adds support for true, false & nil. These each come with a new
separate opcode and are pushed directly on the stack.

Change-Id: I405b5b09496dcf99d514d3411c083e0834377167
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2571
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: BuildkiteCI

users/tazjin/rlox/src/bytecode/mod.rs

@@ -12,7 +12,6 @@ mod vm;
 #[cfg(test)]
 mod tests;
 
-use chunk::Chunk;
 pub struct Interpreter {}
 
 impl crate::Lox for Interpreter {