Refer to new “Integrating provisioning infrastructure services" guide as prerequisites

[ekohl]

Following up on https://github.com/theforeman/foreman-documentation/pull/3530.

Now that we've published a dedicated guide on setting up these resources and removed it from the regular guides we probably broke some links. Looking at it:

$ rg configuring-external-services
guides/common/modules/proc_cloning-satellite-server.adoc
175:For more information, see {InstallingServerDocURL}configuring-external-services[Configuring External Services on {ProjectServer}] in _{InstallingServerDocTitle}_.

guides/common/modules/con_preparing-networking.adoc
23:To configure {Project} to use external DHCP, DNS, and TFTP services, see {InstallingServerDocURL}configuring-external-services[Configuring External Services] in _{InstallingServerDocTitle}_.

Then I also propose we move content out of the provisioning hosts guide and make them prerequisites.

• Preparing networking in Provisioning hosts needs to be thoroughly reviewed. In particular Network resources.
• Creating hosts with UEFI HTTP boot provisioning in Provisioning hosts also needs a review since it tells users to enable TFTP
• Provisioning requirements in Planning for Foreman goes into networking. We need to cross link between the two guides
• Configuring iPXE environment the argument could be made to we should see HTTPboot as an infrastructure service and listed as a prerequisite
• Discovering hosts on a network relies on DHCP. It even mentions the Discovery service and we should debate how to relate these 2

The above is likely an incomplete list.