Debug and trace log messages are often written based on the stderr
logging, where code location is always visible.
journalctl does not show the code location without extra tricks,
which makes user-submitted debug logs from journal more cryptic.
Make journal log more similar to stderr logs by prepending the code
location and log level in the log message when the log topic
level is >= DEBUG.
Previously, `log-patterns.c` was included in two other source files
(`journal.c` and `logger.c`). It was also specified in the sources
list for the libspa-support library, which resulted in the unnecessary
independent compilation of the file, generating "defined but not used"
warnings.
Extract the function definitions into `log-patterns.h` and
use that in `journal.c` and `logger.c`, and remove the inclusion
of `log-patterns.c` from both.
