Add tests for arithmetic / bitwise instructions

[ed255]

• [x] add
• [x] sub
• [x] mul
• [x] divu
• [x] remu
• [x] sltu

Following this structure, add test to compare the emulator and the simulator: https://github.com/ed255/riscu-jolt/blob/ab0bf5a97233942b225859a2bc9153741a6ff999/src/tests.rs#L15-L47