Remove Select trait

I realized that our `select` implementation predated `Simd` being generic over element type, and we don't really need the `Select` trait at all. The function signature is much simpler now (generic over element type, rather than over the entire vector). This did require changing mask select to be a different function, but I think that's fine considering they're not necessarily vectors.

See rust-lang#91867 for more information.

For a data section, the object crate will set SHF_ALLOC by default,
which is exactly what we don't want. Use a debug section instead,
the same as we do for .rmeta.

…ult-methods, r=oli-obk

Mark defaulted `PartialEq`/`PartialOrd` methods as const

WIthout it, `const` impls of these traits are unpleasant to write. I think this kind of change is allowed now. although it looks like it might require some Miri tweaks. Let's find out.

r? `@fee1-dead`

Remove `in_band_lifetimes` for `rustc_passes`

rust-lang#91867

…=lnicola

⬆️ rust-analyzer

r? `@ghost`

…aflow, r=nagisa

Remove `in_band_lifetimes` from `rustc_mir_dataflow`

See rust-lang#91867 for more information.

Sync portable-simd to fix libcore build for AVX-512 enabled targets

Fixes rust-lang#91484 (comment)
cc `@workingjubilee`

Use debug section for .rustc

For a data section, the object crate will set SHF_ALLOC by default, which is exactly what we don't want. Use a debug section instead, the same as we do for .rmeta.

I checked with `objdump -h` that this produces the right flags for ELF.

Fixes rust-lang#92013.

Update stdlib to the 2021 edition

progress towards rust-lang#88638

I couldnt find a way to run the 2018 style panic tests against 2018 so I just deleted them, maybe theres a way to do it that I missed though?