[Quant] Add initial Executorch BackendConfig
Summary: This commit adds the initial `BackendConfig` for
backends to lower to through the Executorch stack. This initial
version is only intended to cover the following set of ops:
quantized::linear_dynamic,
quantized::add,
quantized::batch_norm2d,
quantized::conv2d.new,
quantized::linear,
quantized::conv2d_relu.new,
aten::relu_,
aten::_adaptive_avg_pool2d,
aten::_reshape_alias_copy,
aten::squeeze.dim,
aten::permute
For now, the `BackendPatternConfig` for each of these ops is
the same as the ones for the corresponding ops in the FBGEMM
`BackendConfig`, though this may change in the future.
Reviewers: jerryzh168, vkuzo
Subscribers: jerryzh168, vkuzo
ghstack-source-id: f2339fc9719648bc9970c337c9fe197e327068b3
Pull Request resolved: https://github.com/pytorch/pytorch/pull/85527
