Implement clustered web-session handling

[rymsha]

a second attempt of #6229

[rymsha]

got hit by Ignite bug https://issues.apache.org/jira/browse/IGNITE-11662
Solved it somewhat like described in https://issues.apache.org/jira/browse/IGNITE-11351

[rymsha]

Jetty wants own classloader during deserialization. Fixed it by wrapping SessionData and controlling deerialisation.

[rymsha]

OSGi bundle where jetty de-serialisation happens don't import classes needed (obviously). Workaround: Dynamic-Import

[rymsha]

XP has distinct ports for different servlets. But only one SessionStore. This doesn't work as SessionStore instance must not be shared. Refactored to have SessionStoreFactory

[rymsha]

Unavailable Elasticsearch cluster (In RED state) excludes node from Ignite cluster as well. This generally means RED state of Elasticsearch varnish all data stored Inn Ignite :)
Refactored that part, so Ignite cluster is not stopped if Elasticsearch is down.

[rymsha]

Extracted Ignite to own activator. To be able to control it's lifecycle regardless of "cluster". For instance, don't start it on some nodes
Now can be use in clientMode

[rymsha]

ClusterManager is written in a way that it tend to hang if first available Cluster is not Elasticsearch.
Happens very often when Ignite cluster is there
Slightly refactored ClusterManager so it doesn't wait for Elasticsearch, just starts a scheduler.

[rymsha]

JettyActivator written in a way that it start without Dispatchers. And all dynamically added ones will fail.
Also WebsocketActivator assumes Jetty always has XP dispatcher, which is not true during reconfiguration
Refactored JettyActivator so it only activities when all DispatchServlets in-place. WebsocketActivator gets its XP ServletContext registered by JettyActivator.

[rymsha]

Another issue deserves own bug report.in cluster application stopping/stopped events come to browsers even when only one node in a cluster stopped. This should ugly "connection lost" in ContentStudio, but actually everything is functional
Reported #7589

[rymsha]

SessionWrapper was holding reference indefinitely to HttpSession leaving no room for proper handling of invalidated by timeout sessions. See how bad it is here jetty/jetty.project#3913 (comment)
Refactored to rely on Servlet Container

[rymsha]

JCache now version 1.1.1 to simplify OSGi bundling

[rymsha]

Need to understand how WebSockets are affected jetty/jetty.project#3981

Also, probably require to update Jetty again jetty/jetty.project#3913 (Updated Jetty now #7579)

[rymsha]

incorporated into #7921