Adagio: use auto seat name instead of hardcoded "adagio"

[osazos]

This PR updates the Adagio adapter’s MakeBids() function to stop hardcoding "adagio" as the seat name, which currently prevents the use of bidder aliases.

[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, ef8a8da96060136a23657d3632faf71083766345

adagio

Refer here for heat map coverage report

github.com/prebid/prebid-server/v3/adapters/adagio/adagio.go:21:	Builder		100.0%
github.com/prebid/prebid-server/v3/adapters/adagio/adagio.go:28:	MakeRequests	80.0%
github.com/prebid/prebid-server/v3/adapters/adagio/adagio.go:52:	MakeBids	93.8%
github.com/prebid/prebid-server/v3/adapters/adagio/adagio.go:114:	getBidType	100.0%
github.com/prebid/prebid-server/v3/adapters/adagio/adagio.go:129:	getBidExt	100.0%
total:									(statements)	92.6%