build: add --enable-more-logging configure option

build: add --enable-more-logging configure option

NM core uses nm-logging which is entirely configurable at runtime.
Other components use glib-logging, which can also be partly configured
via G_MESSAGES_DEBUG.

It makes sense to have a compile time option to enable some
logging statements that are only useful for heavy debugging.

For glib-logging, this is a way to enable/disable extra logging.
For nm-logging, we could alternatively configure a least log-level
that is enabled at compile time (that way, we could configure to prune all
LOGL_TRACE logging). While that might be useful (too), this gives
an alternative way to disable/enable logging.

Add a configure option --enable-more-logging and a NM_MORE_LOGGING define
for that.

If we don't find this useful after a while, we can simply remove it,
because our logging statements are not part of a "stable" behavior.