Make SIMD intrinsics available in const-contexts

[sayantn]

successor to #146568, this PR actually makes the SIMD intrinsics const, and modifies the tests to test the const-eval implementations

r? @tgross35 ig (although feel free to reassign, this is not anything targeted really)

[rustbot]

Some changes occurred to the platform-builtins intrinsics. Make sure the
LLVM backend as well as portable-simd gets adapted for the changes.

cc @antoyo, @GuillaumeGomez, @bjorn3, @calebzulawski, @programmerjake

The Miri subtree was changed

cc @rust-lang/miri

Some changes occurred to the intrinsics. Make sure the CTFE / Miri interpreter
gets adapted for the changes, if necessary.

cc @rust-lang/miri, @RalfJung, @oli-obk, @lcnr

[rustbot]

tgross35 is currently at their maximum review capacity.
They may take a while to respond.

[RalfJung]

Cc @Amanieu

[programmerjake]

I know this wasn't there originally, but maybe we should add a test that requires being added in the proper order to return the right result? something like 1.0e20f32 + 1.0 - 1.0e20 - 1.0 == -1.0

[sayantn]

that seems like a nice idea, but I really don't want to add new tests in this PR - this is pretty big by itself anyway

[programmerjake]

other than that idea for a new test, lgtm

View changes since this review

[bors]

☔ The latest upstream changes (presumably #148507) made this pull request unmergeable. Please resolve the merge conflicts.

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[rust-log-analyzer]

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  PR_CI_JOB: 1
  SKIP_SUBMODULES: src/gcc
  IMAGE: tidy
##[endgroup]
error: PRs changing the `nightly` channel should be sent to the `master` branch!
##[error]Process completed with exit code 1.
##[group]Run echo "disk usage:"
echo "disk usage:"
df -h
shell: /usr/bin/bash --noprofile --norc -e -o pipefail {0}