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ARROW-17849: [R][Docs] Document changes due to C++17 for centos-7 users (#14440)

* `configure` checks that `R CMD config CXX17` is defined and exits early if not
* README and install.Rmd discuss system dependencies; install.Rmd includes a bash script to run once to configure your CentOS 7 machine to install arrow. Confirmed that this works manually via docker.
* Updated `r_docker_configure.sh` to use that script logic, so our CI should confirm too.
* Various cleanups in nixlibs.R: remove checks for gcc 4.8/4.9 all over, updated system requirements check to handle case of devtoolset-8 but no openssl/curl
* Unrelated purge of windows build script handling for rtools35

Lead-authored-by: Neal Richardson <neal.p.richardson@gmail.com>
Co-authored-by: Jacob Wujciak-Jens <jacob@wujciak.de>
Signed-off-by: Neal Richardson <neal.p.richardson@gmail.com>