Move attribute and keyword docs from std to core

[jschillem]

Move the documentation for attributes and keywords into the core crate. Apart from strictly moving the module, I had to make a few small changes to certain docs to avoid using std types when possible, as well as fixing a few suggestions related to linking to primitives.

Pre-requisite for work on #157604.

r? @GuillaumeGomez

Verified documentation using:
./x doc library/core and ./x doc library/std, as well as running doc-tests for both crates.

[rustbot]

Thanks for the pull request, and welcome! The Rust Project is excited to review your changes, and you should hear from @GuillaumeGomez (or someone else) some time within the next two weeks.

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[GuillaumeGomez]

Thanks!

@bors r+ rollup

[rust-bors]

📌 Commit e5d79ed has been approved by GuillaumeGomez

It is now in the queue for this repository.

[JonathanBrouwer]

💔 I suspect this PR failed tests as part of a rollup
@bors r-

After fixing the problem, consider running a try job for the failed job before re-approving.

Link to failure: #158389 (comment)

[rust-bors]

This pull request was unapproved.

This PR was contained in a rollup (#158389), which was unapproved.

View changes since this unapproval

[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.

[GuillaumeGomez]

@bors try job=test-various

[rust-bors]

💔 Test for 6850d53 failed: CI. Failed job:

• try - test-various (web logs, enhanced plaintext logs)

[jschillem]

@bors try job=test-various

[rust-bors]

@jschillem: 🔑 Insufficient privileges: not in try users

[jschillem]

@GuillaumeGomez it seems the doc tests are failing for WASM due to the explicit_tail_calls feature being unsupported. I added a commit to ignore these tests. Not sure if this is the best approach and its strange to me how these tests passed when in std.

[jschillem]

(...) its strange to me how these tests passed when in std.

https://doc.rust-lang.org/rustc/platform-support/wasm32-wasip1.html#testing
The failing target was not being tested for libstd but is for libcore.

[jschillem]

@rustbot review

[rust-log-analyzer]

The job x86_64-gnu-tools failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

...............................F.................. (50/144)
.................................................. (100/144)
............................................       (144/144)

======== tests/rustdoc-gui/go-to-collapsed-elem.goml ========

[ERROR] line 40
    at `tests/rustdoc-gui/go-to-collapsed-elem.goml` line 21: Error: Node is detached from document: for command `click: "//*[@id='search']//a[@href='../test_docs/struct.Foo.html#method.must_use']"`
    at <file:///checkout/obj/build/x86_64-unknown-linux-gnu/test/rustdoc-gui/doc/test_docs/struct.Foo.html?search=t_use>


<= doc-ui tests done: 143 succeeded, 1 failed, 0 filtered out

Error: ()