[backport] Add benchmark for the number of minimum cpu cores (#5127) (#5613)

This backports https://github.com/paritytech/polkadot-sdk/pull/5127, to
the stable branch.

Unfortunately https://polkadot.subsquare.io/referenda/1051 passed after
the cut-off deadline and I missed the window of getting this PR merged.

The change itself is super low-risk it just prints a new message to
validators that starting with January 2025 the required minimum of
hardware cores will be 8, I see value in getting this in front of the
validators as soon as possible.

Since we did not release things yet and it does not invalidate any QA we
already did, it should be painless to include it in the current release.

(cherry picked from commit a947cb83)