Client-side support for new UIA events

[SamBent]

Description

Fixing two problems with the recent work to support new UIA events (#4850):

1. New events were not delivered to client-side code. More precisely, UIA delivers the events to our internal client-side listener, but it lacked the plumbing needed to forward the event to user client-side listeners (decoding the event type, converting event args from native to managed, etc.).
2. The TextRange argument to the ActiveTextPositionChanged event was set to a raw ITextRangeProvider, instead of a wrapper.

Customer Impact

1. Managed clients don't receive the new events.
2. An ActiveTextPositionChanged listener that calls one of the ITextRangeProvider methods crashes the target app.

Regression

Problems only affect usage of the new events.

Testing

Ad-hoc. New test cases are being added.

Risk

These fixes are required.