Closes: https://github.com/filecoin-project/lotus/issues/11679
* Introduce a `moved:"To.New.Config"` tag which prints a stderr warning when
you use one of these, but will move any set value to the new location if the
new location isn't already set itself.
* Look for `X is DEPRECATED` to hold certain fields back from documentation.
* Use `toml:"omitempty"` to prevent the default config output from having these
deprecated values.
