Summary:
Storing the `__PRETTY_FUNCTION__` for logging has an unreasonable cost on (non-strippable) binary size for debug builds, as different template instantiation will produce long, demangled, and non-mergeable strings.

If necessary, all the information is retrievable from the debug info (even if the function is inlined), where it's stored in much more efficient form. So, switch to `__func__`, which is stripped.

Reviewed By: yfeldblum, luciang

Differential Revision: D27825136

fbshipit-source-id: d499084c7e7b24db1cd46aa2b03f4a590c6eddc3