Because this now always takes place at the start of the function, we can just
use the normal `alloca` method and then initialize each bitmap immediately.

This patch also moves bitmap setup out of the `mcdc_parameters` method, because
there is no longer any particular reason for it to be there.

This clearly distinguishes individual decision-depth indices from the total
number of condition bitmaps to allocate.

…alloc

… r=workingjubilee

Implement ptr_as_ref_unchecked

Implementation of rust-lang#122034.

Prefixed the feature name with `ptr_` for clarity.

Linked const-unstability to rust-lang#91822, so the post there should probably be updated to mentions the 3 new methods when/if this PR is merged.

Fix cannot usage in time.rs

Fix a small grammar error in usage of cannot in time.rs errors

… r=workingjubilee

default_alloc_error_hook: explain difference to default __rdl_oom in alloc

Though I'm not sure if that is really the reason that this code is duplicated. On no_std it may already be possible to call user-defined code on allocation failure.

…ion, r=fmease

Add raw identifier in a typo suggestion

Fixes rust-lang#68962

coverage: Clean up creation of MC/DC condition bitmaps

This PR improves the code for creating and initializing [MC/DC](https://en.wikipedia.org/wiki/Modified_condition/decision_coverage) condition bitmap variables, as introduced by rust-lang#123409 and modified by rust-lang#124255.

- The condition bitmap variables are now created eagerly at the start of per-function codegen, via a new `init_coverage` method in `CoverageInfoBuilderMethods`. This avoids having to retroactively create the bitmaps while doing codegen for an individual coverage statement.
- As a result, we can now create and initialize those bitmaps using existing safe APIs, instead of having to perform our own unsafe call to `llvm::LLVMBuildAlloca`.
- This PR also tweaks the way we count the number of condition bitmaps needed, by tracking the total number of bitmaps needed (max depth + 1), instead of only tracking the maximum depth. This reduces the potential for subtle off-by-one confusion.

…workingjubilee

Describe and use CStr literals in CStr and CString docs

Mention CStr literals in the description of both types, and use them in some of the code samples for CStr. This is intended to make C string literals more discoverable.

Additionally, I don't think the orange "This example is not tested" warnings are very encouraging, so I have made the examples on `CStr` build.

CI: remove `env-x86_64-apple-tests` YAML anchor

This PR removes the only remaining anchor in the definition of CI jobs. This anchor made it annoying to copy-paste the job e.g. to PR CI.

Fixes: https://rust-lang.zulipchat.com/#narrow/stream/242791-t-infra/topic/How.20do.20you.20edit.20PR.20CI.20to.20test.20PR.20now.3F

r? ``@pietroalbini``