Vastly speed up provider documentation publishing (#33792)

* Vastly speed up provider documentation publishing

Publishing documentation is quite slow when preparing multiple
provider documentation - and this is mostly because we are serializing
copying of directories and checking if the directories are present.
Hhowever we can easily speed it up by parallelising the publishing
per-package.

This will speed up both CI and release-manager's docs publishing
step (vastly).

Co-authored-by: Elad Kalif <45845474+eladkal@users.noreply.github.com>