[v25.2.x] Adding support for private networking config for serverless

[vbotbuildovich]

Backport #28180 to branch v25.2.x. This issue was created as a placeholder because the original PR's commit(s) could not be automatically cherry-picked.
Here are the commands to execute:

git checkout v25.2.x
git checkout -b manual-backport-28180-v25.2.x-777
git cherry-pick -x 85e1e3cbc8 466912029a 1cf5deb2ba a4b7e81801 b1be922ab6 e5ee6e7082 ce3aefc2d1

git push origin manual-backport-28180-v25.2.x-777
gh pr create \
  --title "[v25.2.x] Adding support for private networking config for serverless" \
  --base "v25.2.x" \
  --label "kind/backport" \
  --head "manual-backport-28180-v25.2.x-777" \
  --draft \
  --repo "redpanda-data/redpanda" \
  --milestone "v25.2.x-next" \
  --body "Backport of PR https://github.com/redpanda-data/redpanda/pull/28180 "