docs: added "billions" doc in Distribute>Essentials

Adding building for billions guide to Distribute>Essentials section
covering content on building for low-bandwidth and low-cost.

Cherry-picked out of master for release on current (pre-DODS) release branch.

Cherry-pick2: Build failed. Now moving to DODS branch to try building there.
Removing a "Related Resources" block because it doesn't render. Will patch back in in a future release.

Bug: 27643355
Change-Id: Icb5089fe5528265f4e00b9b9e390a6743c691549