Fix: logging: unhandled error in *_FMT macros

Fix: logging: unhandled error in *_FMT macros

Coverity reports:

1508779 Uncaught exception
If the exception is ever thrown, the program will crash.

In lttng::​sessiond::​rotation_thread::​_thread_function(): A C++ exception
is thrown but never caught (CWE-248)

The *_FMT macros, which use fmtlib, don't handle the case where
fmt::format throws. This can happen, in particular, when an invalid
format string is used.

The macros are modified to log the exception and abort.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: I7f4a066b418a9d544a679f773df7e94640755f47