Some life cycle fixes
This goes on top of the non WIP parts of !755 (merged) and fixes life cycles of hash tables and list models along with some other cleanups.
* history-box: No need to unparent the stack
GTK cleans up for us
* calls-manager: Don't leak hash tables
For that to work we need to hold the ref on self->origins_flat
as it would otherwise be cleaned up twice.
* history-box: Keep ref on list model
The gtk_*list_model_new() functions are `transfer: full` for the model.
* calls-manager: Keep ref on list-models
The gtk_*list_model_new() functions are `transfer: full` for the model.
Since we keep accessing the underlying models we keep the refs for clear
ownership and drop them in finalize.
* call-record-row: Drop superfluous cast
* call-record-row: Use g_clear_signal_handler
glib is recent enough nowadays
* util: Drop now unused macros