This commit rewrites the way that weirds are logged and fixes a number
of issues on the way. Most prominently, flow weirds now actually log
information about the flow that they occur in (before this change, they
only logged the name of the weird, which is only marginally helpful).
Besides restructuring how weird logging works internally, weirds can now
also be generated by calling Weird::weird with the info record directly,
allowing more fine-granular passing of information. This is e.g. used
for DNS weirds, which do not have the connection record available any
more when they are generated (before data like the connection ID was
just not logged in these instances).
Addresses BIT-1578
