Optimize log query

[bonny]

Some things to consider:

Remove the usage of SQL_CALC_FOUND_ROWS. Many posts suggest that it's faster to run two queries instead.
Also, since MySQL 8.0.17 SQL_CALC_FOUND_ROWS and found_rows() are deprecated.

References:

• https://dev.mysql.com/doc/refman/8.0/en/information-functions.html#function_found-rows
• https://www.percona.com/blog/2007/08/28/to-sql_calc_found_rows-or-not-to-sql_calc_found_rows/
• https://stackoverflow.com/questions/186588/which-is-fastest-select-sql-calc-found-rows-from-table-or-select-count

Also, when checking for new rows, do the full query need to run, could we not only use a subset of the query?

[bonny]

Related issue in WordPress trac:

• https://core.trac.wordpress.org/ticket/47280