[ntuple] Split RNTupleView<T, bool> in two classes

[jblomer]

Explain what you would like to see improved and how.

The boolean template in RNTupleView<T, bool> steers whether or not the view is owned by the user. It would be more clear to use two different classes.

ROOT version

master

Installation method

n/a

Operating system

n/a

Additional context

No response