Track how long do embedding methods take

[pau557]

It would be great if when an EmbeddingComposite is used, the sampleset.info["timing"] dictionary was updated with the EmbeddingComposite overheads. The thing that I'm interested the most for benchmarking purposes is the unembedding stage. I would like to know how long did every chain_break_method take in order to find the optimal combination of quantum and classical resources.

[arcondello]

See https://github.com/dwavesystems/dwave-samplers/issues/22 for a discussion of timing in samplers. This should fit into that model.