Update Query Analytics UI to clarify estimated results on MySQL 'explain' response where we modified original query

Now the MySQL explain response is a JSON with this structure:

{
   "explain_result": []byte,
   "explained_query": string,
   "is_dml": bool
}

Explained query has the query that was explained.
If it is a SELECT, it is going to be equal to the original query but if is_dml is true, we should show a message saying that the query was changed by an equivalent SELECT.

There is a feature build that can be used for testing: https://github.com/Percona-Lab/pmm-submodules/pull/1741