Stale topic tags should be noindex'd

[jonoaldersonwp]

Support topic tag archive pages, like ​https://wordpress.org/support/topic-tag/_765258526/, should be noindex'd under any of the following criteria:

• The last posts in any member topic was over 2 years ago.
• Only one post exists.
• All member posts meet their own, individual noindex criteria (i.e., stale posts, no responses, etc).

[dd32]

In 8639:

Support Forums: Add noindex, follow robots headers to a bunch of various archives and pages..

Fixes #4324, #4338, #3955, #4283, #4384, #4329.