Please not: There is not strong consensus that we should enable rustfmt

This is a tracking issue for pursuing the idea and helping reach consensus.

Previous discussion on rustfmt:

• The original issue: Files are not formatted with latest rustfmt #172
• Could we get a contribution/style guideline and Makefile? #685
• Rust Style Conventions #692

The main blockers to getting consensus

1. Showing that the results of rustfmt'd code are acceptable to folks [1]
2. Working out how to manage the massive changes in a safe reviewable manner

This is likely an organization wide change because it will painful for devs to have to configure their environment differently for different repos in the org?

[1] implies agreeing on a configuration of rustfmt that is acceptable to folks.