Non-voting replicas provide low-latency stale reads in all regions for REGIONAL tables

[rmloveland]

See also:

• Document "non-voting replicas" #9039
• Replace the "geo-partitioned replicas" topology pattern with its high-level multi-region equivalent #9265
• Replace the "geo-partitioned leaseholders" topology pattern with its high-level multi-region equivalent #9266
• Replace the "follower reads" topology pattern with its high-level multi-region equivalent #9269
• Add docs for ALTER TABLE .. SET LOCALITY .. #9301
• Add docs for ALTER TABLE .. {ADD,REMOVE} NON-VOTING REPLICAS #9302
• Update CREATE TABLE docs with CREATE TABLE .. SET LOCALITY #9303
• The REGIONAL table locality pattern supports row-level homing #9709

[rmloveland]

I think this issue can be closed since follower reads work on REGIONAL tables "as expected" and we also have the following docs:

• Follower Reads main page
• Follower reads "topology"
• non-voting replicas in architecture docs
• num_voters and the other new MR fields in zone config docs

There is also follow-up work on follower reads that will be done via #9870 and #10377, but I would argue what we have now meets the needs for the release w.r.t. "non-voting replicas".

@awoods187 please re-open if you disagree with the above!