Increase default number of partitions for Bulk Action and StreamWorkManager queues

Some bulk actions are configured with very low defaultPartition resulting in a bulk command that hard to scale.

For instance this the case for the recomputeViews and recomputeThumbnails bulk actions that define 2 partitions.
The number of partition limits the maximum concurrency for the Nuxeo cluster, by default 2 is not enough to process large volume.
This must be increased to 6 by default.

The same thing, for the Stream WorkManager where the number of partitions is proportional to the maxThreads defined in the Work queue,
with the exception when using maxThreads=1, in this case, we don't want any concurrency.
Some Work queues should not be configured with maxThreads=1: pictureViewsGeneration, renditionBuilder, and videoConversion.
using maxThreads=2 instead will results in creating 6 partitions (maxThreads * nuxeo.stream.work.over.provisioning.factor default over provisioning factor being 3).