cpp-common: Add common exceptions

cpp-common: Add common exceptions

Add `bt2_common::{End, Error, MemoryError, TryAgain}` exception classes
to use in in-tree components and elsewhere. Each exception inherits a
C++ standard exception that I believe matches more closely in meaning.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: I7335465f2377e032ae9706108708e35d78d38e6e
Reviewed-on: https://review.lttng.org/c/babeltrace/+/7918
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>