Add timing information to candidate network generation, mps generation

[machristie]

Since the backend restricts how many concurrent requests are running, it can be hard to figure out how long a request actually took once it started being processed. This issue would report to the user how long the request took, and if appropriate, break down the request processing time into subcomponents.

However, the main motivation for this is to tease out how much time of the mps generation is spent generating a candidate network. If the candidate network is reused for the mps generation, then that won't be much of a factor. Or, the frontend could string together generating the candidate network and then do the mps generation and know explicitly how long each part takes, so that's another idea.