hg-core: add function timing information This change makes use of the newly added logging infrastructure to trace the execution time of some important calls. This approach is very much complementary to using a profiler and will not guard against out-of-order execution or other kinds of compiler optimizations. That said, it is useful to get a rough high-level idea of where time is spent. Differential Revision: https://phab.mercurial-scm.org/D8253