Bug Description

Its follow-up enhancement for #353 and feedback #345 (comment)

If we set up multisite in WP then it will save the option in their sub-site DB. Like if you have two sub-site then the plugin option will save the option in the below tables.

wp_options - Main site option table
wp_2_options - 1st Sub-site option table
wp_3_options - 2nd Sub-site option table

The current uninstaller route only deletes options from the main site perflab_modules_settings but it will not remove the option for its subsite.

Steps to reproduce

1. Setup Multisite
2. Create 2-3 subsite
3. Download and activate the Performance Lab plugin for all sites.
4. Delete plugin
5. Check the DB perflab_modules_settings option for sub-site.

Screenshots