Rustdoc doesn't require the build artifacts to generate the docs, and
especially in the case of rustc, it greatly increases the time needed to
run the build.

Don't build the compiler and standard library before documenting them

Rustdoc doesn't require the build artifacts to generate the docs, and
especially in the case of rustc, it greatly increases the time needed to
run the build.

r? ```@Mark-Simulacrum``` cc ```@steffahn```

rustc: Remove local variable IDs from `Export`s

Local variables can never be exported.

…oalbini

Remove extra unshallow from cherry-pick checker

This is already done by https://github.com/rust-lang/rust/blob/13db8440bbbe42870bc828d4ec3e965b38670277/src/ci/init_repo.sh#L32-L36 on the beta channel, and git throws an error if you attempt to unshallow an already non-shallow repository.

r? `@pietroalbini`

generic_const_exprs: use thir for abstract consts instead of mir

Changes `AbstractConst` building to use `thir` instead of `mir` so that there's less chance of consts unifying when they shouldn't because lowering to mir dropped information (see `abstract-consts-as-cast-5.rs` test)

r? `@lcnr`

Rework DepthFirstSearch API

This expands the API to be more flexible, allowing for more visitation patterns
on graphs. This will be useful to avoid extra datasets (and allocations) in
cases where the expanded DFS API is sufficient.

This also fixes a bug with the previous DFS constructor, which left the start
node not marked as visited (even though it was immediately returned).

Commit written by `@nikomatsakis` originally, cherry picked from several commits in work on never type stabilization, but stands alone.

…umeGomez

Allow missing code examples in trait impls.

Excludes Trait implementations from the items that need to have doc code examples when using the `rustdoc::missing_doc_code_examples` lint.

For details see #88741

fixes #88741

r? ``@jyn514``

rustdoc: Cleanup `clean` part 1

Split out from #88379.

These commits are completely independent of each other, and each is a fairly
small change (the last few are new commits; they are not from #88379):

- Remove unnecessary `Cache.*_did` fields
- rustdoc: Get symbol for `TyParam` directly
- Create a valid `Res` in `external_path()`
- Remove unused `hir_id` parameter from `resolve_type`
- Fix redundant arguments in `external_path()`
- Remove unnecessary `is_trait` argument
- rustdoc: Cleanup a pattern match in `external_generic_args()`

r? `@jyn514`

explicitly link to external `ena` docs

we currently do not link to the docs of `ena`: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_infer/infer/struct.InferCtxtInner.html#method.const_unification_table