lib: merge common CTF IR part with the remaining implementation

lib: merge common CTF IR part with the remaining implementation

This patch merges the common part of the CTF IR implementation with the
rest of it, making it one. This will make it easier to modify this
implementation since it's not split in two.

Support for common CTF IR conversion specifiers is removed in
`lib-logging.c` (see updated `lib-logging-internal.h` documentation).

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>