Rename adapters to bidders in alternate bidder codes config

[pm-nilesh-chate]

Rename adapters to bidders in alternate bidder codes config w.r.t #2174

Old pbs.yaml example:

account_defaults:
  alternatebiddercodes:
    enabled: true
    adapters:
      pubmatic:
        allowedbiddercodes: [groupm]
      appnexus:
        allowedbiddercodes: [*]

New pbs.yaml example:

account_defaults:
  alternatebiddercodes:
    enabled: true
    bidders:
      pubmatic:
        allowedbiddercodes: [groupm]
      appnexus:
        allowedbiddercodes: [*]

[bsardo]

LGTM

[SyntaxNode]

Thank you putting this PR so quickly. I plan to merge it in later today. Let's leave a little more time for other folks from the community to comment on this breaking change (for a feature released 2 weeks ago). There's a thread on the Prebid Slack as well asking for feedback. There were no concerns voiced at the Prebid Server Committee meeting last week.