proposal: new JS interstate object

[Mikhail (oo-sleeper)]

Main idea here is to convert

engineProtocol
	FilterOut    bool
	PartitionKey string
	Data         any
	HTTPHeaders  map[string]string

to

engineProtocol
	FilterOut    bool
	PartitionKey string
	Data         map[string]any
	HTTPHeaders  map[string]string

so it is much clearer what interstate data could be, plus it allows for future improvements on the transformations in general

Note: this is a breaking change, because it is changes behaviour around how we handle arbitrary string as input to JS script

Used to be

// x.Data is a 'string' type
function main(x) {
   let newVal = "Hello:" + x.Data;
   x.Data = newVal;
   return x;
}

now it must be

// x.Data is an 'object' (map[string]any) type
function main(x) {
   let newVal = "Hello:" + x.Data['Data'];
   x.Data['Data'] = newVal;
   return x;
}