Updates to /direction/ecosystem, removing Marketplace

Removing Marketplace from Ecosystem categories, and replacing with a new section explaining rationale on the change.

Required Approvals

• VP of Product @sfwgitlab
• VP of Product Strategy @markpundsack
• The Product Director relevant to the stage group(s) @joshlambert
• The Engineering Director relevant to the stage group(s) @cdu1
• CEO @sytses

/cc @edjdev @clefelhocz1 @meks