The e2e core framework and subpackages of e2e framework are defined.
The subpackages can import the core framework, but the core framework
should not import the subpackages. We've defined this dependency rule
after circular depencency issue happened.
This adds TODOs to understand what we should in this rule.
This continues the work in
https://github.com/kubernetes/kubernetes/pull/81426 by also moving the
logger_test.go, moving the log helper code from util.go to log.go (a
more logical place, as it is only used there) and updating comments.
We tried to separate logger functionality as subpackage of e2e test
framework, but we've recognized that should be core functionality
and we should keep it as core of e2e test framework after facing
circular dependency issues.
So this adds log.go back to core of e2e test framework. In addition,
this makes volume sub package use the core logger as a sample.
