Refactor reformat all source files with `clang-format`

[adamkewley]

Estimate: 1-2d

So that there is less ambiguity about whether something is formatted correctly.

[adamkewley]

Dropping from next release - a few new bugfix tickets (e.g. #645, #644) pushed time out of the schedule and I need to drop ~6 days of development time from the milestone.