remove UnevaluatedConstKind::def_id

[khyperia]

this is some of the const side of #152245

not quite a full removal, there's still some spicy things such as UnevaluatedConstKind::def_span remaining that won't quite work for new non-DefID UnevaluatedConstKind cases, but IMO this is the bulk of the work, and feature-specific things can deal with their quirks in their own PRs when they know their own use cases.

r? @BoxyUwU

self-reminder: file an issue on what to do about rustc_public's handling of the raw DefIds in rustc_public AliasTy/AliasConst

[rustbot]

Some changes occurred in const_evaluatable.rs

cc @BoxyUwU

changes to the core type system

cc @lcnr

Some changes occurred in abstract_const.rs

cc @BoxyUwU

This PR changes rustc_public

cc @oli-obk, @celinval, @ouz-a, @makai410

Some changes occurred in match checking

cc @Nadrieril

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri, @RalfJung, @oli-obk, @lcnr

[rustbot]

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[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.