Use MKL Rewrite pass in convolution microbenchmark
cc: @penpornk @cantonios 
Instead of hard-coding whether to use Eigen or MKL node in https://github.com/tensorflow/tensorflow/blob/master/tensorflow/core/kernels/conv_ops_benchmark_test.cc leverage MklLayoutRewritePass class to decide whether to rewrite node or not. 

This also aligns with change present in this PR: https://github.com/tensorflow/tensorflow/pull/60026 where decision whether to rewrite node is decided based if computation cost amortizes overhead cost.