Fixesnushell/nushell#13689
# Description
Respect user-defined `$env.NU_LOG_FORMAT` and `$env.NU_LOG_DATE_FORMAT`
Additionally I fixed `nu_with_std!()` macro (it was not working
correctly)
# User-Facing Changes
Users now may set `$env.NU_LOG_FORMAT` and `$env.NU_LOG_DATE_FORMAT` in
`env.nu` and it will work even if `use std` is used after that.
# Tests + Formatting
Added a couple of tests for the new functionality.
# After Submitting