Convert basic_network_configuration.md to include version 9.0

[sspencerwire]

• This change cleans up the left-hand TOC by reducing it back to one document again.
• Used version 9.0 as the first version listed, per the results of the documentation poll
• Added meta to include version 9.0
• Moved Introduction to the top and made it generic for both releases (8.6 and 9.0)
• Moved Prerequisites beneath Introduction for a better overall structure
• checked document formatting after changes were made. OK

Author checklist (Completed by original Author)

• Contribution a good fit for the Rocky project? Title and Author MetaTags inserted ?
• Is this a non-English contribution?
• If applicable, steps and instructions have been tested to work on a real system
• Did you perform an initial self-review to fix basic typos and grammatical correctness

Rocky Documentation checklist (Completed by Rocky team)

• 1st Pass (Check that document is good fit for project and author checklist completed)
• 2nd Pass (Technical Review - check for technical correctness)
• 3rd Pass (Basic Editorial Review)
• 4th Pass (Detailed Editorial Review and Peer Review)
• Final pass/approval (Final Review)

[sspencerwire]

Nothing much new here. Simply a consolidation of the two documents into one.