Operator should manage caefeederreset

[stefanbethke]

Is your feature request related to a problem? Please describe.
From time to time, it might be necessary to run caefeederreset, to re-index all content.

Describe the solution you'd like
The procedure to reset the CAEFeeder is somewhat involved.

In the simple case of just re-indexing all content:

1. Issue the cm resetcaefeeder command with the correct settings to tell the CAEFeeder to forget all indexed content and start fresh.
2. Restart the CAEFeeder

Of course, this has to be done for both the preview and the live CAEFeeders.

This procedure will update all existing content, but will not remove entries from the index that do not exist in the content anymore. If you would like to also remove outdated entries, you need to have the CAEFeeder build a fresh Solr core. If you would like that fresh core to be built while the CAE is still using the old core, the procedure is quite a bit more involved:

1. Issue the cm resetcaefeeder command with the correct settings to tell the CAEFeeder to forget all indexed content and start fresh.
2. Change the configuration for the CAEFeeder so it will build a new core. Changing the config of the StatefulSet will restart the pod, and kick off the re-index.
3. Monitor the progress of the re-indexing and wait until all content has been indexed.
4. Shut down the CAEFeeder
5. Tell Solr to swap the new and the old core.
6. Remove the old core (which now has the new name)
7. Reconfigure the CAEFeeder to use the standard core name again and restart it.

Again, this needs to happen to both the preview and the live CAEFeeder.
The operator should:

• detect and gracefully handle any problems,
• allow the admin to abort the re-index operation and restore the config to its standard state with just one core.

Describe alternatives you've considered
It is possible to do this by hand, but it's very involved and error-prone.