Asserting on the generated JSON alone would pass just as happily with a
misspelled sink argument, which Serilog ignores in silence - and silently not
rolling is the bug. These build a real logger from Libation's own config and
write until it rolls, including a test that pins the old unbounded behaviour so
a future change to the defaults cannot quietly restore it.
Co-authored-by: rmcrackan <rmcrackan@gmail.com>
