package/rabbitmq-server: drop package

The packaged version has a number of security issues, newer versions require
erlang 23+ and nobody has stepped up to maintain it since the issues were
reported:

http://lists.busybox.net/pipermail/buildroot/2022-November/656230.html



So drop the package and add legacy handling for it.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>