When comparing objects which get printed to very long strings (e.g.
collections like vectors), it's much more readable if they get printed
to individual lines. Differences are much easier to spot then.

This CL refactors the CHECK/DCHECK macros to print the left hand side
and right-hand side in individual lines if any of them is longer than 50
characters.

To that end, the {PrintCheckOperand} method (only used from
{MakeCheckOpString}) is changed to return the string directly instead of
printing to an output stream.

R=mlippautz@chromium.org

Change-Id: I6e24a5cbfeb1af53fa0aca2828e23f642b15569c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1991866Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65705}