Add and adopt a handful of utilities to make common generation tasks (includes, namespaces, indentation) easier.
<rdar://problem/102682125>
Pull request: https://github.com/WebKit/WebKit/pull/6825
Committed 257046@main (6060568db87c): <https://commits.webkit.org/257046@main> Reviewed commits have been landed. Closing PR #6825 and removing active labels.