chore: use provided tag insertion method

[naripok]

Summary

Closes https://github.com/AirGrid/rmap/issues/1459

Type of change

• Bugfix

Description of change

Use loadExternalScript instead of custom code for tag module loading

Other information

@ydennisy

[naripok]

@ydennisy I did what they asked, but we have a problem which I'm not sure how to tackle yet:

EDIT:
Well, I found this in their tests, and I think it may pose a problem with how we interpolate the module url for the publishers...

    it('only allows whitelisted vendors to load scripts', function () {
      adLoader.loadExternalScript('someURL', 'criteo');
      expect(utilsLogErrorStub.called).to.be.false;
      expect(utilsinsertElementStub.called).to.be.true;
    });

If we need a fixed url to be whitelisted, then we're gonna need to whitelist all the possible publisher specific urls, and update the whitelist (wherever it is, haven't found yet) every time we add a new publisher... :(

EDIT:
Hmm, the docs look to imply that we need a more lengthy process in order to be able to load our module...
It involves asking for a prebid's maintainer to clone this repo, adding code there, then loading from it in the adapter. If I understood correctly, obviously...

[naripok]

Another consideration, @ydennisy .
Prebid's loadExternalScript accepts an attributes parameter, which it sets to the script being loaded.
I've tried moving our accountId, publisherId and apiKey to it, but it won't set the attributes in the same fashion we do now, and it breaks our tests.
As I'm not sure of the implications of it, I'm leaving the attribute setting as is, now done in the callback function called as continuation in the loadExternalScript function.