e2e: allow customizing genesis parameters on the manifest #3961
Description
Similarly to #3832, we should be able to set all genesis parameters using the manifest.
At the moment we can customize some of them, using variables like BlockMaxBytes, VoteExtensionsUpdateHeight, etc. (see this method).
Ideally, we should be able to set any value. Which should not be particularly complex since the genesis is a JSON file and it should be easy to parse any genesis field from the manifest, which is also a JSON file.