R1:bd939782001e

Count and report skipped documents from "bin/search index"

Summary:
Ref T12450. There's currently a bad behavior where inserting a document into one search service marks it as up to date everywhere.

This isn't nearly as obvious as it should be because `bin/search index` doesn't make it terribly clear when a document was skipped because the index version was already up to date.

When running `bin/seach index` without `--force` or `--background`, keep track of updated vs not-updated documents and print out…