Document r/o and r/w PRserv and HASHserv in the templates

This adds sections for the PRserv and HASHserv in the local.conf templates (for r/o upstream).
Also we add comments to the r/w part that is reserved for CI.

Change-Id: Id39b11bc9664b441f5dcae3646259401b5d9a6aa
Signed-off-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/29945
Tested-by: Jenkins Job builder account
ci-image-boot-test: Jenkins Job builder account
ci-image-build: Jenkins Job builder account