Tests settings should be defined in the test source code itself
because conceptually the framework is a separate entity that not all
test authors can modify.

Using the new framework/config code also has several advantages:
- defaults can be set with less code
- no confusion around what's a duration
- the options can also be set via command line flags

While at it, a minor bug gets fixed:
- readConfig() returns only defaults when called while
  registering Ginkgo tests because Viperize() gets called later,
  so the scale in the logging soak test couldn't really be configured;
  now the value is read when the test runs and thus can be changed

The options get moved into the "instrumentation.logging"
resp. "instrumentation.monitoring" group to make it more obvious where
they are used. This is a breaking change, but that was already
necessary to improve the duration setting from plain integer to a
proper time duration.