Ability to monitor progress of ADMIN CHECK INDEX | TABLE

## Feature Request

**Is your feature request related to a problem? Please describe:**
When checking index consistency on large tables (several TB), ADMIN CHECK INDEX takes many hours or even days. It is hard to estimate how long it will take to finish or even if it is working at all.

**Describe the feature you'd like:**
A metric with % of work complete when running ADMIN CHECK INDEX and/or TABLE.

Suggestion from @dveeden:

> Yes would be nice to have a progress column in information_schema.processlist and/or have some progress information in the logs (e.g. every 10m). Something that knows the total number of rows from stats and the number of rows checked etc. So yes, please create an issue on GitHub.

**Describe alternatives you've considered:**
Haven't found any way to get this information.