UOE-12550 Adding placementid support for Nativo

[pm-isha-bharti]

No description provided.

[github-actions]

Code coverage summary

Note:

• Prebid team doesn't anticipate tests covering code paths that might result in marshal and unmarshal errors
• Coverage summary encompasses all commits leading up to the latest one, cc876eb

nativo

Refer here for heat map coverage report

github.com/PubMatic-OpenWrap/prebid-server/v3/adapters/nativo/nativo.go:27:	Builder			100.0%
github.com/PubMatic-OpenWrap/prebid-server/v3/adapters/nativo/nativo.go:34:	MakeRequests		83.3%
github.com/PubMatic-OpenWrap/prebid-server/v3/adapters/nativo/nativo.go:80:	MakeBids		94.4%
github.com/PubMatic-OpenWrap/prebid-server/v3/adapters/nativo/nativo.go:117:	getMediaTypeForImp	100.0%
total:										(statements)		91.5%

[Pubmatic-Supriya-Patil]

@pm-isha-bharti I think no need to redefine impExt in each loop unless you're adding multiple fields conditionally.
we can update to :

if ext.Bidder.PlacementId == "" {
continue
}

impExtJSON, err := json.Marshal(impExtNativo{
	Nativo: openrtb_ext.ImpExtNativo{
		PlacementId: ext.Bidder.PlacementId,
	},
})
if err != nil {
	return nil, []error{err}
}

imp.Ext = impExtJSON