Add a new column for docs.total in CAT indices API

[ppf2]

Currently, we have two columns for doc counts in /_cat/indices API:

docs.count
docs.deleted

It can be confusing to the end users (esp. those who deal with frequent updates) because docs.counts does not represent the total number of documents in the index. It only represents the "live" documents. docs.deleted represents the "dead" documents that are deleted and waiting to be purged (still occupy disk storage).

So to calculate the % of deleted docs in an index, the user will have to use docs.deleted/(docs.deleted+docs.count).

Have we considered adding a new column (but not display it by default so that it will not be a breaking change).

docs.total (total)
docs.count (live)
docs.deleted (deleted)

For users who only care about the "live" documents, they will certainly be fine to continue to use docs.count.

[elasticmachine]

Pinging @elastic/es-core-features (Team:Core/Features)