The `--replace` argument for `substitute` and `substituteInPlace` was
deprecated in e07a2fab7f. Updating all
references in the nixpkgs manual to use `--replace-fail`.
The following changes are made:
- Document how `wrapType2` and `wrapType1` are the same thing.
- Expand on how `wrapType2` works and additional arguments it uses.
- Document `extract` and show how it's used in combination with
`wrapType2`.
- Provide full working examples using the new admonition syntax.