* initialize all log-related features in a new wp_log_init() function
* remove the ability to change the log patterns later, as the log
topics are not referenced by the log system and there is no way to
re-initialize them with different levels (we can still implement this
in the future, if necessary, though)
* introduce the notion of a "global log level", referenced by all topics,
and make the topics know if they have a custom level or not, like in
pipewire; this is necessary to be able to set the level in the config
file, which is read later by pw_context / WpCore.
The intention is to make checks for enabled log topics faster.
Every topic has its own structure that is statically defined in the file
where the logs are printed from. The structure is initialized transparently
when it is first used and it contains all the log level flags for the levels
that this topic should print messages. It is then checked on the wp_log()
macro before printing the message.
Topics from SPA/PipeWire are also handled natively, so messages are printed
directly without checking if the topic is enabled, since the PipeWire and SPA
macros do the checking themselves.
Messages coming from GLib are checked inside the handler.
An internal WpLogFields object is used to manage the state of each log
message, populating all the fields appropriately from the place they
are coming from (wp_log, spa_log, glib log), formatting the message and
then printing it. For printing to the journald, we still use the glib
message handler, converting all the needed fields to GLogField on demand.
That message handler does not do any checks for the topic or the level, so
we can just call it to send the message.
Previously we were mapping SPA ERROR to GLib WARNING and
SPA WARN to GLib MESSAGE, which has been causing some confusion.
After some careful consideration, it makes sense to change that and
leave the GLib MESSAGE level as something to be avoided. With that
change, WIREPLUMBER_DEBUG=M will still enable the MESSAGE level,
but WIREPLUMBER_DEBUG=2 will only enable the WARN level and it will
take WIREPLUMBER_DEBUG=3 to enable both the INFO and MESSAGE levels.
This allows for WIREPLUMBER_DEBUG="D" which avoids users having to
remember which numerical value the various levels have. The strings to
select are the ones printed by the logger, i.e. UECWMIDT.
Also rename the intermediate lua api table WpDebug -> WpLog
Keeps things more consistent with the function names (wp_log*),
with the lua api (Log.*) and with pipewire using log.{h,c} as well.
After all, these functions are for logging...
