Verify numeric instructions

[zixuanzh]

As per issue #18

parity-wasm checks types for const operators but not for binary as specified in the spec.

We simulated the stack to check for types and hence we added a new validator interface that takes in a mutable self reference. We also use a self defined enum instead of String for error handling and propagation as advised by the documentation.

[jakelang]

@zixuanzh CI is failing because you need to run cargo fmt. just FYI

[jakelang]

@zixuanzh CI seems to be a version behind on rustfmt. will fix that.

edit: actually that doesn't seem to be the problem. trying to find out why fmt is still freaking out.

edit 2: Are you sure you are using the correct version?

[zixuanzh]

I am running on 1.32.0-nightly, fmt fails at deployer.rs etc in CI, it passes CI when I only commit verify-instructions related files.

[jakelang]

@zixuanzh is this ready or WIP? Please add the respective label.

Also please rebase.

[zixuanzh]

@jakelang it should be ready as it is unless @Steampunkery has something to add, we don't have access to add labels.

[axic]

I think this looks good in general, great work @Steampunkery and @zixuanzh!

[axic]

@Steampunkery @zixuanzh can we take over this PR or do you think you'll have some resources to work on this in the next while?

[zixuanzh]

@axic please proceed, we are unlikely to work on this in the immediate future. thanks