See #36285 which mistakenly added documentation for the whole C++ API, while
some of it is meant to be and stay private as it's not exposed to scripts.
The access modifiers and method prefix were not used properly.
Cleanup code, and rename wrong `group_name` parameters to `method`, as it's a
method name which is being broadcast.
This is a very old class from pre-open source days, chances are that it was
just forgotten and not meant to be kept as is and undocumented.
Which means that reduz' beloved style which we all became used to
will now be changed automatically to remove the first empty line.
This makes us lean closer to 1TBS (the one true brace style) instead
of hybridating it with some Allman-inspired spacing.
There's still the case of braces around single-statement blocks that
needs to be addressed (but clang-format can't help with that, but
clang-tidy may if we agree about it).
Part of #33027.
