[RF] Inconsistent prints from some RooStats classes

[VanyaBelyaev]

Explain what you would like to see improved and how.

some RooStats classes, e.g. RooStats::AsymptoticCalculator perform prints using all three printing ways within O(10) lines, e.g.

1. printf
2. std::cout
3. oocoutP

As result, it makes impossible to control the output verbosity.
Would it be possible to convert all std::cout and printf into ROOT/RooFit prints ?

ROOT version

6.35/1
I am using LCG dev3 nightly build from cvmfs

Installation method

cvmfs, LCG dev3 nightly slot

Operating system

Linux, lxplus.cern.ch

Additional context

No response