* ls: Remove allocations by eliminating collect/clones
* ls: Introduce PathData structure
- PathData will hold Path related metadata / strings that are required
frequently in subsequent functions
- All data is precomputed and cached and subsequent functions just
use cached data
* ls: Cache more data related to paths
- Cache filename and sort by filename instead of full path
- Cache uid->usr and gid->grp mappings
https://github.com/uutils/coreutils/pull/2099/files
* ls: Add BENCHMARKING.md
* ls: Document PathData structure
* tests/ls: Add testcase for error paths with width option
* ls: Fix unused import warning
cached will be only used for unix currently as current use of
caching gid/uid mappings is only relevant on unix
* ls: Suggest checking syscall count in BENCHMARKING.md
* ls: Remove mentions of sort in BENCHMARKING.md
* ls: Remove dependency on cached
Implement caching using HashMap and lazy_static
* ls: Fix MSRV error related to map_or
Rust 1.40 did not support map_or for result types
