Make sure the log level on the chained logger is the same as ours.
Makes PIPEWIRE_DEBUG=3 make run print debug again.
This used to work because the log level was parsed and set before the
loggers were created and chained, and so they all got the same level.
Now that the level can be changed with metadata at runtime, we can't
really update all past loggers so let the journal logger copy the
level itself.
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.
