…5281)

Motivation:

In our testsuite we often just wrapped a byte[] and passed it to the
write method. While this works it also might end up not testing often
with direct buffers. We should make this a bit more random and so cover
direct and heap buffers. The idea popped up when reviewing
#15231

Modifications:

- Add new static helper method that will either return a wrapped buffer
or a direct buffers in a random fashion
- Use this method to allocate buffers

Result:

More random testing of heap / direct buffers