also in Miri, "base tag" -> "root tag"

…n-backport-nominations, r=GuillaumeGomez

meta: notify #t-rustdoc Zulip stream on backport nominations

In July '23, it was decided to handle rustdoc-specific backport nominations in t-rustdoc meetings going forward ([Zulip announcement](https://rust-lang.zulipchat.com/#narrow/stream/266220-t-rustdoc/topic/T-rustdoc.20backports/near/374828518)). However, t-rustdoc meetings are far too infrequent for them to address nominations on time (contrary to the weekly t-compiler meetings).

Hence GuillaumeGomez and I came to the conclusion that {beta,stable}-nominated rustdoc PRs should be dealt with on a case by case basis, e.g. on Zulip.

This PR attempts to partially automate this process. ~~Sadly, `triagebot` is not quite as flexible has I've hoped. Blocked on `triagebot` improvements (see the `FIXME`s in this PR).~~ (Fixed in rust-lang/triagebot#1791).

r? GuillaumeGomez

…, r=oli-obk

interpret: pass MemoryKind to adjust_alloc_base_pointer

Another puzzle piece for rust-lang/miri#3475.

The 2nd commit renames base_pointer -> root_pointer; that's how Tree Borrows already calls them and I think the term is more clear than "base pointer". In particular, this distinguishes it from "base address", since a root pointer can point anywhere into an allocation, not just its base address.

rust-lang#124018 has been rolled up already so I couldn't add it there any more.

r? ``@oli-obk``

…ze, r=jhpratt

Stabilize `const_io_structs`

This PR stabilizes `const_io_structs`.

Tracking issue: rust-lang#78812.
Implementation PR: rust-lang#78811.

FCPs already completed in the tracking issue.

Closes rust-lang#78812.

``@rustbot`` label: +T-libs-api

r? libs-api

Add another expression to weird-exprs.rs

I'm almost feeling bad for this but I decided I don't.
Feel free to close if you don't approve.