PyUtils: Try to work around another diff-root dictionary issue.
In some contexts, we see failures when diff-root tries to retrieve objects from the TTree that are related to cling synthesizing incorrect forward declarations. These can be avoided by ensuring that dictionaries are loaded first, so change RootUtils.dump to do that.
Trying to fix failures in the derivation CI tests see in the gcc14 build. See ATEAM-1000.