Change all g_test_init calls in the testsuite to avoid the macro, so they work regardless of G_DISABLE_ASSERT.
The calls used old bugzilla URLs and nobody cared about that. So apparently they are very unused. There's also a potential conflict between gitlab and bugzilla URLs and what base bug to use there. The old usages have been converted to comments.
Adapt all our tests and examples to the new initialization api.
In particular, we're testing corner cases with empty rectangles here.
