refactor: use `os.ReadDir` for lightweight directory reading
refactor: use `os.ReadDir` for lightweight directory reading

`os.ReadDir` was added in Go 1.16 as part of the deprecation of `ioutil`
package. It is a more efficient implementation than `ioutil.ReadDir` as
stated here https://pkg.go.dev/io/ioutil#ReadDir.

Signed-off-by: Eng Zer Jun <e94bff687675f33b892ede8d3a0a0eab27d6715c@gmail.com>

helm/helm,bacongobbler/helm,helm/helm,bacongobbler/helm