IX: pass-through ext.ixdiag fields in bid request

[oronno]

This PR implements the pass-through of the ext.ixdiag field from the incoming bid request to the exchange. The existing IX adapter code already sets a few fields in ixdiag and sends them to the exchange, but it does not account for ext.ixdiag from the incoming request. This implementation combines the existing ixdiag fields set by PBS with the ext.ixdiag fields from the incoming request.

[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, 5e9d6a7

ix

Refer here for heat map coverage report

github.com/prebid/prebid-server/v3/adapters/ix/ix.go:42:	MakeRequests			89.2%
github.com/prebid/prebid-server/v3/adapters/ix/ix.go:109:	setPublisherId			100.0%
github.com/prebid/prebid-server/v3/adapters/ix/ix.go:151:	unmarshalToIxExt		100.0%
github.com/prebid/prebid-server/v3/adapters/ix/ix.go:165:	parseSiteId			80.0%
github.com/prebid/prebid-server/v3/adapters/ix/ix.go:175:	createRequestData		100.0%
github.com/prebid/prebid-server/v3/adapters/ix/ix.go:186:	MakeBids			95.1%
github.com/prebid/prebid-server/v3/adapters/ix/ix.go:305:	getMediaTypeForBid		80.0%
github.com/prebid/prebid-server/v3/adapters/ix/ix.go:336:	Builder				100.0%
github.com/prebid/prebid-server/v3/adapters/ix/ix.go:349:	mergeNativeImpTrackers		100.0%
github.com/prebid/prebid-server/v3/adapters/ix/ix.go:373:	marshalJsonWithoutUnicode	83.3%
github.com/prebid/prebid-server/v3/adapters/ix/ix.go:393:	extractVersionWithoutCommitHash	100.0%
github.com/prebid/prebid-server/v3/adapters/ix/ix.go:400:	setIxDiagIntoExtRequest		88.9%
github.com/prebid/prebid-server/v3/adapters/ix/ix.go:449:	moveSid				75.0%
total:								(statements)			91.5%