ISE Plugin "Scripts Containing" does not work most of the time

[AdamNaj]

Expected Behavior

Selecting text in ISE and running the "Scripts containing" plugin should result in finding all scripts containing the selected words.

Actual Behavior

It works less often than it doesn't. I find that reindexing tends to help. But this can be fixed with some changes to the plugin script, which I'll submit in a moment.

Steps to Reproduce the Problem

Install fresh Sitecore or use it for a while without full reindex. Select a phrase and try to use the plugin.

[AdamNaj]

@michaellwest - can you take a look and let me know if you find a problem? Also since XM on-prem is only available in scaled topology I've added ContentManagement as an additional role to serialization config.