chore: add long running test

[Caele]

Motivation

Adds a test for long runnning queries by adding a delay to the mocked engine calls. It currently doesn't properly cancel the call when you press cancel (or the test presses cancel), but it covers the functionality.

@streamside Feel free to clean up this code if you like, had to do some light hacking to get the delay to work without slowing everything down too much.

[streamside]

The intent when writing this was to include all properties on the genericObjects passed to the enigma mocker. The property delay is more of a setting on how it should behave. Down the road there might be conflicts if engine also provides a property with the same name. I suggest to introduce an options object - which for now includes only the delay setting - to the exposed API:

fromGenericObjects(genericObjects, options)

The delay option would be "global" and effect all generic objects being mocked. If more granular control is desired the dev would be able to delay individual objects / functions.

The code looking up the generic object by its qId didn't become that pretty with the findAsync(). Another option would be to return the qId along with the mock when creating the mocks (around line 32 in get-object-mock.js). The lookup to find the correct object would become easier and no need to add qId on the mock.

Let me know your thoughts about it and if I should make any changes to the code.

[streamside]

@Caele I have updated the PR with two changes. (1) delay added in options object the enigma-mocker which effects all async calls, and (2) lookup of the mocks via qId is simplified. Feel free to take a look!