[hadd] do not print info to stderr

[ferdymercury]

This Pull request:

Changes or fixes:

Fixes #19479

[github-actions]

Test Results

    21 files      21 suites   3d 10h 14m 3s ⏱️
 3 223 tests  3 223 ✅ 0 💤 0 ❌
65 909 runs  65 909 ✅ 0 💤 0 ❌

Results for commit c9d3d62.

[silverweed]

I don't think we should print the Info() messages on stdout; I'd rather have an option to silence the output altogether if that's the desired outcome (we already have a verbosity option: we can simply not emit Info() if verbosity is less than 1 or something)

[pcanal]

Currently this PR is awaiting additional feedback in the issue (it is not clear what the underlying issue really is).

[ferdymercury]

There was a change of behavior, in ROOT 6.32 hadd printed info messages to std::cout
In ROOT 6.36 they are printed to std::cerr, so I guess the user is surprised or confused by this change.
Maybe the easiest is to document this change in the release notes and close isssue as won't fix.

[pcanal]

close isssue as won't fix.

Before doing that, I would like to hear from the user what explicitly bother them and how, so we can clarify the situation from their point of view.