The container image inherits kernel.core_pattern from the host. When
the host pipes core dumps to a handler (e.g. Ubuntu's apport), that
handler does not exist or work correctly inside the container, so core
dumps are silently lost.
Override any pipe-based core_pattern with a file-based pattern that
writes directly to /var/lib/scylla/coredump/. The override is attempted
both from the entrypoint (scyllasetup.coredumpSetup) and from
scylla-server.sh when running as root; it succeeds only when the
container has write access to /proc/sys/kernel/core_pattern and is
silently skipped otherwise.
Fixes: SCYLLADB-1366
Closesscylladb/scylladb#29337
