[v23.3.x] Add forward iterator to async_for_each

[vbotbuildovich]

Backport #16676 to branch v23.3.x. Note that this issue was created as a placeholder, since the original PR's commit(s) could not be automatically cherry-picked.
Here are the commands to execute:

git checkout v23.3.x
git checkout -b vbotbuildovich/backport-16676-v23.3.x-586
git cherry-pick -x c667749ed2c1ae3f042d20e0c0218217b1096b3c

git push origin vbotbuildovich/backport-16676-v23.3.x-586
gh pr create \
  --title "[v23.3.x] Add forward iterator to async_for_each" \
  --base "v23.3.x" \
  --label "kind/backport" \
  --head "vbotbuildovich/backport-16676-v23.3.x-586" \
  --draft \
  --repo "redpanda-data/redpanda" \
  --milestone "v23.3.x-next" \
  --body "Backport of PR https://github.com/redpanda-data/redpanda/pull/16676 "

[travisdowns]

Merged in #16688.