Fix clippy warnings

[yubiuser]

Fixes a clippy warning that occured in recent tests regarding map_clone (https://rust-lang.github.io/rust-clippy/master/index.html#/map_clone) and file creation without explicite defining truncation behavior (https://rust-lang.github.io/rust-clippy/master/index.html#/suspicious_open_options)

[yubiuser]

The last commit addressed changes in the beta toolchain that are a consequence of the expansion of redundant import checking. I removed the duplicate imports, another way would be to disable the warning. There is some discussion ongoing regarding the change: https://github.com/rust-lang/rust/issues/121315 https://github.com/rust-lang/rust/issues/121708

[roderickvd]

Thanks a lot for this, great to have the build pass again!