The issue about `config.txt` files is that they contains paths:
* to configuration files, which are in the source tree
* to the dynamic plugins, which are in the build tree
Solution:
* copy all configuration files into the build tree
* all those paths are about the build tree
* tests run from the build tree, no from the source tree anymore
Some changes in the parameters names.
Add a fuzzer to fuzz the configuration file format.
Add the infrastructure to configuratin callbacks.
Add an helper to map LRU cache indexes to names.
Extend internal unit tests to handle multiple configurations.
As some examples, add tests about:
* disabling some protocols
* disabling Ookla aggressiveness
Every configurations data is stored in a dedicated directory under
`tests\cfgs`
