Clearing search index clears all push sources

Problem/Motivation

When you clear content from one Search API push source it clears content from all push sources connected to the same Coveo Push source. This is a limitation of the Coveo bulk delete API.

Steps to reproduce

Proposed resolution

Until Coveo has a solution there's not much to be done. We can't include queries with our delete operation.

As a workaround, when clearing Coveo push sources, find all SearchAPI sources connected to the same backend and set them to re-index. This will at least make sure all content is re-populated.

Remaining tasks

User interface changes

API changes

Data model changes