Using a new ".configlist" file format that allows specifying
a list of CNI network configurations to run, add new libcni
helper functions to call each plugin in the list, injecting
the overall name, CNI version, and previous plugin's Result
structure into the configuration of the next plugin.
Chaining sends different config JSON to each plugin, but the same
environment, and if we want to test multiple noop plugin runs in
the same chain we need a way of telling each run to use a different
debug file.
highlights:
- NetConf struct finally includes cniVersion field
- improve test coverage of current version report behavior
- godoc a few key functions
- allow tests to control version list reported by no-op plugin
