* Remove unnecessary `#[allow]` annots
Reduce the number of lint exceptions that are not necessary with the
current state of the code (or more recent toolchain)
* Remove dead code from `FileStructure` in nu-command
* Replace `allow(unused)` with relevant feature switch
* Deal with `needless_collect` with annotations
* Change hack for needless_collect in `from json`
This change obviates the need for `allow(needless_collect)`
Removes a pessimistic allocation for empty strings, but increases
allocation size to `Value`
Probably not really worth it.
* Revert "Deal with `needless_collect` with annotations"
This reverts commit 05aca98445.
The previous state seems to better from a performance perspective as a
`Vec<String>` is lighter weight than `Vec<Value>`
