Prebid core: fix adUnits for auction at the time requestBids is called

[dgirardi]

Type of change

• Bugfix

Description of change

If a publisher calls pbjs.addAdUnits or pbjs.removeAdUnit after calling requestBids, those calls might have an effect on ongoing auctions - depending on whether any module needs to defer the start of the auction (for example, if consentManagement needs to look up consent data).

This changes requestBids to always use the adUnits that were defined at the moment it's called.

Other information

Closes #8628

[jsnellbaker]

Tagging @snapwich to possibly review the new code in the hook.js, to see if it would have any strange side-effects with the internals of the hook package.

[snapwich]

from a fun-hooks perspective i don't think there should be any issue copying the methods from one function to another. i don't quite understand why that is necessary here, couldn't you just clone the adunits in requestBids to begin with without the use of this delegate?

either way i think this should work.

[dgirardi]

@snapwich there are various "before" hooks on requestBids, with many of them also falling back to the global adUnits, so I think to do what you say I'd need to add another before hook with higher priority than all of them. The main body of requestBids runs too late.

The high-priority hook was my first attempt, but I found it too hard to test, because a lot of "unit" tests already modify the global hook configuration.

[mmoschovas]

lgtm