chore: cleanup Cargo.toml and rm perl

[nyurik]

This PR is a part of the #4406 per @tgross35 suggestion

• Remove Cargo settings that are identical to the defaults (per Cargo recommendations)
• Fix perl-based method to extract MSRV
• Note that the order of the values is such as to make it easier to switch to the inherited ones from workspace once MSRV is bumped

@rustbot label +stable-nominated

[rustbot]

r? @tgross35

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[tgross35]

Thanks!

[nyurik]

This is weird - FreeBSD-13 / nightly keeps failing with a seg fault - https://cirrus-ci.com/task/5609497042878464?logs=test#L300 ... Was this ever a problem before? Note that there is no code changes...

+ cargo test --target i686-unknown-freebsd --workspace --features extra_traits -- --skip check_style
Segmentation fault (core dumped)

[tgross35]

FreeBSD 13 has a spurious segfault, unrelated to this change of course. It may be related to #3998 but I'm not sure why it isn't consistent.