Fix `CodeGenerationFormat` to not add extra indentation, leave trailing spaces when adding newlines, or indent empty lines

[roopekv]

This fixes multiple issues with CodeGenerationFormat. Files were re-generated with each commit, so the differences in formatting caused by each change to CodeGenerationFormat should be easy to review.

Fix CodeGenerationFormat to not add extra indentation

• Indentation used to be all over the place when formatting children to be separated by newline, this should fix it.

Fix CodeGenerationFormat to not leave trailing spaces when adding newlines

• Formatting children to be separated by newline used to leave spaces after each line's comma, this should trim them.

Fix CodeGenerationFormat to not indent empty lines

• ensuringTwoLeadingNewlines used to add indented newlines, resulting in empty lines being indented. Not anymore.

[roopekv]

@ahoppen is this good to go now?

[ahoppen]

Yes, let’s 🚢it

[ahoppen]

@swift-ci Please test

[ahoppen]

The macOS test failures are unrelated to your changes. I’m looking into them.

[ahoppen]

Sorry, there’s a merge conflict now. Could you rebase?

[roopekv]

Sure, just a moment.

[roopekv]

Done

[ahoppen]

@swift-ci Please test

[ahoppen]

@swift-ci Please test

[ahoppen]

@swift-ci Please test macOS

[ahoppen]

@swift-ci Please test macOS

[ahoppen]

@swift-ci Please test macOS