PubMatic: Pass imp.ext.gpid to SSP

[AvinashKapre]

[github-actions[bot]]

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, 77e15a6569c1809a81c2b3d954b5ba6df06728ce

pubmatic

Refer here for heat map coverage report

github.com/prebid/prebid-server/v2/adapters/pubmatic/pubmatic.go:85:	MakeRequests				93.4%
github.com/prebid/prebid-server/v2/adapters/pubmatic/pubmatic.go:190:	validateAdSlot				91.3%
github.com/prebid/prebid-server/v2/adapters/pubmatic/pubmatic.go:233:	assignBannerSize			100.0%
github.com/prebid/prebid-server/v2/adapters/pubmatic/pubmatic.go:241:	assignBannerWidthAndHeight		100.0%
github.com/prebid/prebid-server/v2/adapters/pubmatic/pubmatic.go:249:	parseImpressionObject			91.7%
github.com/prebid/prebid-server/v2/adapters/pubmatic/pubmatic.go:340:	extractPubmaticExtFromRequest		96.7%
github.com/prebid/prebid-server/v2/adapters/pubmatic/pubmatic.go:392:	getAlternateBidderCodesFromRequestExt	100.0%
github.com/prebid/prebid-server/v2/adapters/pubmatic/pubmatic.go:410:	addKeywordsToExt			85.7%
github.com/prebid/prebid-server/v2/adapters/pubmatic/pubmatic.go:424:	MakeBids				90.7%
github.com/prebid/prebid-server/v2/adapters/pubmatic/pubmatic.go:506:	getNativeAdm				90.9%
github.com/prebid/prebid-server/v2/adapters/pubmatic/pubmatic.go:528:	getMapFromJSON				100.0%
github.com/prebid/prebid-server/v2/adapters/pubmatic/pubmatic.go:540:	populateFirstPartyDataImpAttributes	100.0%
github.com/prebid/prebid-server/v2/adapters/pubmatic/pubmatic.go:553:	populateAdUnitKey			100.0%
github.com/prebid/prebid-server/v2/adapters/pubmatic/pubmatic.go:568:	populateDctrKey				85.0%
github.com/prebid/prebid-server/v2/adapters/pubmatic/pubmatic.go:618:	getStringArray				100.0%
github.com/prebid/prebid-server/v2/adapters/pubmatic/pubmatic.go:631:	getBidType				100.0%
github.com/prebid/prebid-server/v2/adapters/pubmatic/pubmatic.go:651:	Builder					100.0%
total:									(statements)				93.1%