Add local_bound attribute support to conv ops

This includes both respecting the local_bound attribute in the reference
model and generating tests with local_bound=True and local_bound=False
for floating point types. For non-floating point types, we always set it
to False.

Signed-off-by: IanTayler <ian.taylerlessa@arm.com>
Change-Id: Ifa47b6df31b9142835f48da00b595b89c7082734