Backport of Fix panic caused by parsing `json.Number` values for TypeCommaStringSlice fields into release/1.8.x (#14741)

* no-op commit due to failed cherry-picking

* port over ParseCommaStringSlice json.Number fix from go-secure-stdlib

* add changelog entry

(cherry picked from commit cec77a20dc8deb514f635064b73a4299085eafec)
Co-authored-by: temp <temp@hashicorp.com>
Co-authored-by: Chris Capurso <1036769+ccapurso@users.noreply.github.com>