Hide ConvParams struct from ConvUtils.h (#89059)
It isn't actually used outside of Convolution.cpp, so no reason
to publish it. I intend to turn this into a template, so moving
it with the method definitions is very convenient.
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/89059
Approved by: https://github.com/SherlockNoMad
