Add Coroutine Support: YIELD and RESUME

Add coroutine support to your VM in C.

Requirements:

• Define a Coroutine struct with its own PC, stack, stack pointer, call frames, frame count, and a state enum (CREATED, RUNNING, SUSPENDED, DEAD)
• Add OP_COROUTINE opcode that creates a coroutine object with a given function address
• Add OP_YIELD opcode that saves the current VM state into the active coroutine and returns to the caller
• Add OP_RESUME opcode that activates a coroutine, restoring its state
• The main VM should track an active_coroutine pointer; when null, the main thread runs
• Implement a producer coroutine that yields numbers 1 through 5
• Implement a consumer (main program) that resumes the producer and prints each yielded value
• Print coroutine state transitions (CREATED -> RUNNING -> SUSPENDED -> DEAD)
• Show the producer-consumer pattern working correctly

Test:

• Show coroutine creation and state
• Show YIELD suspending execution
• Show RESUME restoring execution
• Show producer-consumer pattern output