[v23.3.x] CORE-7338 license: add enterprise_license_expiry_sec metric

[vbotbuildovich]

Backport #23367 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-23367-v23.3.x-95
git cherry-pick -x 78de1c702ef22c1becb876913674b9c5fa7de31b 1c8f66b467b0b5e84de6e6c424fbe65e825f5e98 edb5f48493aaec25ebcb10f35eb26b3ad5ae1a10 c44d9d8f53222dc4c50063cafc8ff020dc4e586d baece2ccd6c9986a85c1af108dbb5b8387e85f1f

git push origin vbotbuildovich/backport-23367-v23.3.x-95
gh pr create \
  --title "[v23.3.x] CORE-7338 license: add `enterprise_license_expiry_sec` metric" \
  --base "v23.3.x" \
  --label "kind/backport" \
  --head "vbotbuildovich/backport-23367-v23.3.x-95" \
  --draft \
  --repo "redpanda-data/redpanda" \
  --milestone "v23.3.x-next" \
  --body "Backport of PR https://github.com/redpanda-data/redpanda/pull/23367 "

[BenPope]

Fixed by #23468