Allow users to change default Snapshot behaviour of collections

[vepadulano]

Explain what you would like to see improved and how.

As proposed in the following forum post:
https://root-forum.cern.ch/t/how-to-stop-rdataframe-from-changing-column-type-from-std-vector-double-to-root-rvec/58971/3

ROOT version

Any

Installation method

Any

Operating system

Any

Additional context

No response

[vepadulano]

Hint: we need to call this function with vector2rvec=false, this means properly propagating the argument through the call stack.

root/tree/dataframe/src/RDFUtils.cxx

Lines 222 to 223 in 5612a4d

	std::string ColumnName2ColumnTypeName(const std::string &colName, TTree *tree, RDataSource *ds, RDefineBase *define,
	bool vector2rvec)