[FEAT] Allow to only show one or a set of pools at diagram load time

[NathalieC]

Let pass a list of ids and/or names related to the participant in the BPMN semantic related to the pool(s) that will be displayed.

Discussions in progress. We should define the API and the best way to manage it internally.

Note: the original request was different, we decided to reduce the scope of the feature

By default, the library displays the bpmn file, meaning, all diagrams and pools defined in the file.
By configuration, the developer integrating the library (Fred) could define that it only displays one pool, whose id will be passed as a parameter.
By configuration, Fred could also define that it displays a pool and all its called processes (provided they are in the same diagram). Again, he will use parameters to pass the pools' ids to the lib.
In the implementation example, we should be able to show that:

• if the pool id passed as a parameter is a called process, Fred can implement a "navigation up", to the calling pool.
• if the pool id passed as a parameter is a process with call activities, Fred can implement a "navigation down" to the called process
• if both, then Fred could implement both navigations.

Linked to #422

[tbouffard]

mxgraph resources
mxGraph example that hide some elements that exist in the model
https://jgraph.github.io/mxgraph/javascript/examples/layers.html and https://github.com/jgraph/mxgraph2/blob/mxgraph-4_2_0/javascript/examples/layers.html

We tried to make pool parent of lanes and lane parent of other bpmn elements. So making pool not visible in the mxgraph model should hide the children BPMN elements.
Alternative: after load, filter elements that are stored in the mxgraph model. Less elements in the mxgraph model. --> to be investigated

[tbouffard]

In January, we have provided an example using mxgraph custom code that let hide or collapsed pools.
See process-analytics/bpmn-visualization-examples#124 for screenshots.