Consider shipping System.Private.ServiceModel crossgened

This will shave off roughly 800ms off the first cold request (or multiple requests if many requests are issued while the code is still being jitted).

We also need to investigate why manually crossgen-ing already shipped binaries didn't improve the timing.

Start by investigating how System.Private.ServiceModel is packaged and how manually crossgen-ed shipped binaries were tested. Compare cold-request timing with and without crossgening; done requires explaining the failed manual optimization and establishing whether shipping crossgened binaries delivers the reported improvement.

Written by the indexing model from the issue text.