[Reproducers] Limit logging to calls that cross the API boundary.

We recently moved API logging into the instrumentation macros. This made
that logging is now consistent and abstracted behind a macro for every
API functions, independent of the reproducers. It also means we have a
lot more output. While this is a good thing, it also meant a lot more
noise in the log, from things that aren't always equally interesting,
such as the copy constructor for example.

To improve usability, we should increase the signal-to-noise ratio. I
propose to achieve this by only logging API functions that cross the API
boundary. This is a divergence of what we had before, where a select
number of functions were logged, irregardless of the API boundary, a
concept that was introduced for the reproducers. However, I believe this
is in line with the purpose of the API log.

Differential revision: https://reviews.llvm.org/D60984

llvm-svn: 359016