Optimize indexing slices and strs with inclusive ranges

[Kmeakin]

Instead of separately checking for end == usize::MAX and end + 1 > slice.len(), we can check for end >= slice.len(). Also consolidate all the str indexing related panic functions into a single function which reports the correct error depending on the arguments, as the slice indexing code already does.

The downside of all this is that the panic message is slightly less specific when trying to index with [..=usize::MAX]: instead of saying "attempted to index str up to maximum usize" it just says "end byte index {end} out of bounds". But this is a rare enough case that I think it is acceptable

[rustbot]

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[scottmcm]

As you saw from the PR build failure, if you're touching things like slice_index_order_fail you'll need to look through every mention of those in the repo -- there are a bunch of codegen tests that look for their absence, and you need to make sure that you don't make those tests useless by renaming what they're looking for.

(You probably also need to re-bless some MIR tests that include indexing.)

[rustbot]

The Miri subtree was changed

cc @rust-lang/miri

[oli-obk]

@bors try @rust-timer queue

[rust-bors]

⌛ Trying commit bd63d02 with merge 4249615…

To cancel the try build, run the command @bors try cancel.

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[Kmeakin]

@rustbot ready

[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.