MLBEDSW-6263: Use separate tensors for double buffering

Uses separate tensors for the individual weight buffers
in case of weight double buffering.

Each weight buffer tensor gets its own individual live range.

This patch is a clone of a previously reverted patch, but with some
additional bug fixes applied.

Signed-off-by: Rickard Bolin <rickard.bolin@arm.com>
Change-Id: I868c70d15821eb9f1399186f2da6e7345f6ee343