Setup Swift Format

This MR sets up SwiftFormat for consistent formatting.

To run formatting in Xcode: build the Memri + Build Tools scheme. The normal scheme will not run them (formatting files while developing can interfere with undo/redo amongst other things).

• There is no setup required, Xcode will automatically download and build SwiftFormat (local to the project) the first time you run this.

• Note that the first commit in this MR does the required setup, the second commit is purely applying the formatting changes.

• This was based off the latest dev branch. If you have another branch there are likely to be merge conflicts. To get around this, I recommend ensuring your working copy is committed (so you don't lose any work) and then use git's cherry-pick to add the Setup SwiftFormat commit to your branch. Once you run the formatting and commit your files should be consistent with the dev branch → no merge conflicts.