consider auto-registering vm service protocol registration

[pq]

It would be great to avoid needing to explicitly initialize VM service hooks.

That is, it would be nice to do away w/ the need to call:

logManager.initServiceExtensions();

Thoughts:

1. we could do this proactively in the manager (con: carry the cost of an extra service extension even if it's not used; pro: would work in profile / release and not require any code changes or client footwork)
2. clients could do this (e.g., IntelliJ could use EvalOnDartLibrary to call something like initServiceExtensions()) -- con: only works for apps being debugged