[checker] Add missing Feedback printer (BZ#5587)

This fixes longstanding bug likely introduced in the first `pp` to
`Feedback` migration, namely the checker didn't register a feedback
printer, thus no calls to `Feedback.msg_*` were printed in the
checker.

This closes bug: https://coq.inria.fr/bugs/show_bug.cgi?id=5587

We fix this by adding a custom printer to the checker, this is correct
as the checker owns now the full console, however a cleanup should
happen in any of these two directions:

- all the calls to feedback are removed, and the checker always uses
  its own printing mechanism.

- all the calls to `Format/Printf` are removed and the checker always
  uses the `Feedback` mechanism.

Currently, I have no opinion on this.

0 files changed, 0 insertions, 0 deletions