Stack analzyer

[wz14]

This PR adds a static stack analyzer for Script Builder.

    let mut script = script! (
        OP_ADD
        OP_ADD
        OP_ADD
    );
    let (x, y) = script.get_stack();
    assert_eq!(x, -4);
    assert_eq!(y, -3);

The stack analyzer is tested through groth16 verifier. Most of groth16 verifier can be analyzed staticly, but there still are three changes for dynamic cases, which can be pulled later.

BitVM change list:

• src/fp/inv.rs Line 251: HINT
• src/bigint/std.rs Line 111: HINT
• src/bn254/curve.rs Line 417, Line 442: add one Fp::add(), it's improper to add hint to a big script

https://github.com/wz14/BitVM/tree/analyze_groth16