Vastly speed up provider documentation publishing

[potiuk]

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).

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[potiuk]

I noticed that docs publishing step was super-slow on CI (> 3m on main build) and this was mainly because of serializing publishing for multiple providers).

Parallelising it will increase the speed by 2x for public runners (to ~ 1.5 m if all providers are being built) and ~ 8x on self-hosted runners (~ 25 seconds or so)

Also for Release manager of providers (cc: @eladkal) this should cut waiitng time for "publish-docs" from few minutes to seconds.

[potiuk]

Quite a few images regenerated because I found and corrected a mistake in help of the common "--run-in-parallel" option - it mentioned python but it's used to parallelize many things.

[eladkal]

Nice!!!
This step indeed takes time

[potiuk]

56 seconds instead of 3.5 minutes. Not bad :)