Revise the meaning of "follower reads" in docs

[rmloveland]

Richard Loveland (rmloveland) commented:

Per this conversation about 'follower reads' on a docs PR, going forward we will need to start distinguishing between stale follower reads (what we currently call "follower reads") and strongly consistent follower reads (what you get when you do a SELECT against a GLOBAL table).

Estimated scope of work:

• Start drawing a line between stale vs. strong(ly consistent) follower reads
• (Eventually, maybe in another issue?) Start distinguishing between "exact" and "bounded" staleness
• Possibly other work that falls out based on the above

Jira Issue: DOC-1631