Implement OnExecHook VM API

[Furetur]

Problem

This MR implements the proposed Hooks API from #3415 that can be used for coverage collection, tracing, breakpoints, and etc

Solution

This is a very small change. The main points are as follows:

1. A new field is added to the VM

+	// All registered hooks.
+	// Each hook should never be nil.
+	hooks hooks

2. hooks is a structure meant to store all of the VM hooks:

// OnExecHook is a type for a callback that is invoked
// for each executed instruction
type OnExecHook = func(scriptHash util.Uint160, offset int, opcode opcode.Opcode)

// A struct that contains all VM hooks
type hooks struct {
	onExec OnExecHook
}

3. The default value of the OnExec hooks is a NOP function
4. A VM.SetOnExecHook method is added to register hooks

// SetOnExecHook sets the value of OnExecHook which
// will be invoked for each executed instruction.
// This function panics if the VM has been started.
func (v *VM) SetOnExecHook(hook OnExecHook) {
	if v.state != vmstate.None {
		panic("Cannot set onExec hook of a started VM")
	}
	v.hooks.onExec = hook
}

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.10%. Comparing base (2280523) to head (a7883c7).
Report is 43 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3460      +/-   ##
==========================================
- Coverage   86.13%   86.10%   -0.04%     
==========================================
  Files         331      331              
  Lines       38470    38564      +94     
==========================================
+ Hits        33138    33207      +69     
- Misses       3804     3827      +23     
- Partials     1528     1530       +2     

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[AnnaShaleva]

@Furetur, any update on this? See also the related comments (#3462 (comment), #3462 (comment)).

[AnnaShaleva]

Also please, pay attention to the PR workflows. Linter job is failing and commit sign-off is required for every commit.

[Furetur]

Hello, @AnnaShaleva!

Thanks for your comments, especially the ones about workflows.

I am currently overloaded with work but I'll do my best to address your comments over the next few days.

[Furetur]

@AnnaShaleva could you please approve the workflow?

[Furetur]

Fixed the 'lint' job (locally). @AnnaShaleva could you please rerun the workflows?

Also, previously the 'coverage' job failed because some token was null. I believe that it was not because of my code

[AnnaShaleva]

Also, previously the 'coverage' job failed because some token was null.

It's just the problem with our Coverage job itself, it doesn't work with outer contributions. So you're right, it's not your fault.

[AnnaShaleva]

Otherwise LGTM.

[roman-khimov]

It's just the problem with our Coverage job itself

It's a feature!

[Furetur]

Seems like I've fixed all the comments, or are there any that I've missed?

[AnnaShaleva]

Also please note that unit-tests are failing:

2024-06-24T16:05:21.9161891Z === RUN   TestCannotSetOnExecHookOfStartedVm
2024-06-24T16:05:21.9162035Z     vm_test.go:135: 
2024-06-24T16:05:21.9162483Z         	Error Trace:	/home/runner/work/neo-go/neo-go/pkg/vm/vm_test.go:135
2024-06-24T16:05:21.9163197Z         	            				/home/runner/work/neo-go/neo-go/pkg/vm/vm_test.go:2782
2024-06-24T16:05:21.9163485Z         	Error:      	Received unexpected error:
2024-06-24T16:05:21.9163733Z         	            	no program loaded

[AnnaShaleva]

@Furetur, could you please update the #3460 (comment) and fix failing tests? This PR is ready to go otherwise, and then we'll continue with #3462.

[AnnaShaleva]

Also, please, add "Close #3415" entry to the PR/commit message for proper GH linking.

[Furetur]

@AnnaShaleva

could you please update the #3460 (comment) and fix failing tests?

Done

[Furetur]

Sorry for the failing unit tests. I've probably "refactored" them a little bit before committing and forgot to rerun them

[Furetur]

Previously the CodeCov job failed because my commit decreased the overall coverage of the entire project. I don't think that my change could have caused those changes

But I've added a test to mptdata_test.go that covers uncovered lines of code

[AnnaShaleva]

Otherwise LGTM.

[Furetur]

Extracted the additional test into a separate PR
#3501