Evaluate concurrency behavior of the proposed Solr ACL indexing design

An ACL indexing scheme for Solr has been proposed in:

https://github.com/nuxeo/nuxeo-solr/tree/master/architecture

We need to evaluate the scalability of the following operations:

• update the ACLs of a high level tree node (with say up to ~10k folder descendants)
• update move one folder from a workspace to another

We also need to evaluate the behavior of Solr under concurrent load with a mix of:

• 80% ACL filtered document search queries with and without sorted results (we need to add modification time date field).
• 18% Document update
• 1% folder move
• 1% ACL update

We need a ramp of CUs with different principal profiles to check the impact on the ACL field query cache usage.

Those scenarii can be prototyped with a bunch of Funkload testcases using the [sunburnt](https://github.com/tow/sunburnt) Solr client lib for python.