[Feature Request]: Support Fluid Framework version 2

[ryanbliss]

Fluid V2 is now in beta, so for Live Share v2 we need to support it as it includes breaking changes.

[huntj88]

We should also use targetClientId where it makes sense to send signals to specific clients instead of all of them

[ryanbliss]

We should also use targetClientId where it makes sense to send signals to specific clients instead of all of them

#795 does this :)