Avoid runtime universe init during startup

[dwijnand]

Instead of initialising the scala reflection runtime universe the first
time a ManagedLogger is created (aka, at start up), let's kick that down
the line and use the cached LogExchange.stringTypeTagSuccessEvent for
def success.

[dwijnand]

Spotted with async-profiler:

That's ManagedLogger creating the runtime universe during startup.

[eed3si9n]

This came up in #153 and #221.
Do you have some before and after comparison number, like loading akka build and exiting several times?

[eed3si9n]

Also note that the "develop" branch for util is now at sbt/sbt - https://github.com/sbt/sbt/blob/develop/internal/util-logging/src/main/scala/sbt/internal/util/ManagedLogger.scala

[dwijnand]

Yeah, I saw. I'll move to sbt/sbt, which helps because I can build an sbt and give you an after number too.

[dwijnand]

OK, in develop the runtime universe is warmed up in the ClassLoaderWarmup (on another thread). Even removing that it gets warmed up by TaskProgress sending a log message and needing a TypeTag for itself. So I stopped there.