[Relay] Move TOpPattern registration for nn.* to C++ (apache#12072)

* [Relay] Move TOpPattern registration for nn.* to C++

Some of the Collage machinery is best tested from C++, but
requires Relay ops to have their "TOpPattern" registered.
However since the nn.* ops register on the Python side tests
can't rely on those ops.

The easy fix is to just move the registration to the
RELAY_REGISTER_OP block. However since kOpaque is the
default I did not preserve those registrations.

There's still a few dozen more exotic ops still registered
on the Python side. I've left them be.

* - D'oh! Even kOpaque ops must be registered.