W-22969158 Update af-* xrefs to target agent-network component

[IsaacEldridge]

IMPORTANT-- for agent network v2 release -- GA is 6/30

The af-* pages moved from anypoint-code-builder to the new agent-network component. Update cross-repo xrefs and fix the #set-up-agent-network-gateways-for-your-target-space anchor to the explicit [[setup-gateways]] ID used in both 1.0 and 2.0.

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