Meta
`Meta` wasn't really serving a distinct purpose in the API, so rolled it into `Man` now that it lazily renders.
This is part of #3354
BREAKING CHANGE: Functions now take ownership
This is an initial implementation with plenty of room to grow, including - Allowing pulling out a subset of the generated man page for greater customization - Subcommand handling - Extra sections - Consolidate argument formatter after #2914 Fixes #552