1.30.1 stable release

I believe this includes all of the relevant pieces from https://github.com/rust-lang/rust/issues/55594. Backports all proceeded smoothly.

cc @rust-lang/release

Remove `cargo new --edition` from release notes.

This was removed at the last minute (#55315, https://github.com/rust-lang/cargo/pull/6216).
Apologies for not catching this.

overlook overflows in rustdoc trait solving

Context:

The new rustdoc "auto trait" feature walks across impls and tries to run trait solving on them with a lot of unconstrained variables. This is prone to overflows. These overflows used to cause an ICE because of a caching bug (fixed in this PR). But even once that is fixed, it means that rustdoc causes an overflow rather than generating docs.

This PR therefore adds a new helper that propagates the overflow error out. This requires rustdoc to then decide what to do when it encounters such an overflow: technically, an overflow represents neither "yes" nor "no", but rather a failure to make a decision. I've decided to opt on the side of treating this as "yes, implemented", since rustdoc already takes an optimistic view. This may prove to include too many items, but I *suspect* not.

We could probably reduce the rate of overflows by unifying more of the parameters from the impl -- right now we only seem to consider the self type. Moreover, in the future, as we transition to Chalk, overflow errors are expected to just "go away" (in some cases, though, queries might return an ambiguous result).

Fixes #52873

cc @QuietMisdreavus -- this is the stuff we were talking about earlier
cc @GuillaumeGomez -- this supersedes #53687

Co-Authored-By: steveklabnik <steve@steveklabnik.com>

We're gonna link to nightly as this didn't make it into the corresponding stable.

Stable release 1.30

This PR also reverts the stabilization of `non_modrs_mods` and the 2018 edition.

r? @Mark-Simulacrum
cc @rust-lang/release

This reverts commit 4d1ec818.

This reverts commit 7f6b6089.

I was reading through the release notes to find something and noticed
some small grammatical and consistency issues.

[beta] Rollup backports

Merged and approved:

* #55231: pick a reference issue for absolute-paths future incompatibility info
* #55224: Use a keyword in raw identifier example

r? @ghost

It would be kind of embarrassing to ship with the "issue TBD" message!

[beta] Rollup backports

Merged and approved:

* #54300: Updated RELEASES.md for 1.30.0
* #54939: rustdoc: don't prefer dynamic linking in doc tests
* #54671: resolve: Scale back hard-coded extern prelude additions on 2015 edition
* #55102: resolve: Do not skip extern prelude during speculative resolution

r? @ghost

This reverts commit e90985ac.

[beta] Bump bootstrap compiler to 1.29.2

r? @Mark-Simulacrum

[beta] back out #53793 - stabilize outlives requirements

Fixes #54467 for beta, looks like a less risky fix than #54701

[beta] Rollup backports

Merged and approved:

* #54851: Fix a regression in 1.30 by reverting #53564
* #54865: Backport 1.29.2 release notes to master
* #54810: Fix dead code lint for functions using impl Trait

r? @ghost

This reverts commit 6ce76aca.

This reverts commit 11e488b6.

This reverts commit 1a1a7f61.

This reverts commit 1908892d.

This reverts commit 21d2a6c9.