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ARROW-16901: [R][CI] Prune R nightly builds (#13453)

This PR adds pruning to the nightly R upload, 14 versions will be kept by default. 

I have removed the `burnett01/rsync-deployments` actions because the use of docker for this was unnecessary and the action can only upload to a remote. This new manual version also utilizes host key checking for which I created `secrets.NIGHTLIES_RSYNC_HOST_KEY` (which should contain the result of ` ssh-keyscan -H nightlies.apache.org 2> /dev/null` and needs to be added to apache/arrow before this can run).  This way we are no longer depending on the action and it's associated Dockerfile (`drinternet/rsync`). 

We might want to refactor this into a local action for use with all nightly upload jobs.

The pruning is not super efficient as we download the whole nightly repository (on cache miss). This could be avoided for the libarrow files, they could possibly be deleted via ssh instead but we need to download all R packages as `tools::write_PACKAGES` needs access to each archive.

Authored-by: Jacob Wujciak-Jens <jacob@wujciak.de>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>