Move pl-build-tools build requirements to platform definitions in puppet-runtime

build_requires lines in puppet-runtime that pull in packages from pl-build-tools are distributed throughout many of the component definitions; These should be moved to the platform definitions wherever possible.

The goal is to let us easily replace requirements for pl-build-tools packages with requirements for native packages, or offer that option. This may let us stop building some pl-build-tools packages entirely, and will make building puppet-agent easier for community members outside of Puppet.

Since puppet-agent inherits its settings from puppet-runtime, we'll make these changes there first, then do the same for puppet-agent.

To make this process less disruptive, we'll move platform-specific configuration from component to platform definitions separately for each group of platforms:

• EL variants
• Debian-based platforms
• Windows
• Solaris
• AIX
• macOS
• Network platforms