This was broken in the config rewrite in Hugo 0.112.0.
The workaround is to be explicit about setting these flag values (even if just using the defaults), e.g.:
```
hugo deploy --invalidateCDN --maxDeletes 256
```
Fixes #11127
Primary motivation is documentation, but it will also hopefully simplify the code.
Also,
* Lower case the default output format names; this is in line with the custom ones (map keys) and how
it's treated all the places. This avoids doing `stringds.EqualFold` everywhere.
Closes #10896
Closes #10620
