+14%: Add an option to disable ElementProbe

[jbdeboer]

ElementProbe sets up an expando on nodes, which we suspect is slow.

There should be an option to disable it entirely, both for experiments and for production tuning.

[jbdeboer]

We saw a ~7% regression due to b7f175b in order to support ElementProbe. Removing it will get those 7% back and then some; for very simple elements, this could be significant (e.g. 25% speedup)

[jbdeboer]

Removing ElementProbe from ElementBinder and ShadowDomComponentFactory sped the TreeComponent benchmark up by 14%

It also reduced memory allocations from 51mb/run to 43mb

This is an easy, high priority fix.

[jbdeboer]

This task involves creating an application-level configuration option (e.g. similar to ScopeDigestTTL) which controls whether or not the ElementProbe is created in ElementBinder, ShadowDomComponetFactory and TranscludingComponentFactory.

Cavaet: ElementProbe is also used in the EventHandler, which is used for on-* events. These events are not in wide use yet, so for a first pass, the configuration option could disable the EventHandler as well.

[jbdeboer]

I'm working on this issue this morning