Update "Content Helper" and "Traffic Boost" strings

[acicovic]

Is your request related to a problem?

After deciding to rename the above features, our mentions of "Content Helper" and "Traffic Boost" should now appear as "Content Intelligence" and "Engagement Boost" in our UIs and documentation.

However, the original naming for both of the features had been in use for a long while, and since the rename was carried out very quickly, our code hasn't been refactored in all places to accommodate for the new naming.

There are strings that have broader implications such as option and filter names. These should be handled accordingly.

Describe the solution you'd like

To keep naming consistent and our codebase up to date, we should update the strings as needed.