FreeBSD and using system limit instead for others.

Because it's never used meaningfully.

Do not re-parse function signatures to suggest generics

This PR uses the existing resolution rib infrastructure to channel the correct span information to suggest generic parameters.  This allows to avoid re-parsing a function's source code.

Drive-by cleanup: this removes useless `FnItemRibKind` from late resolution ribs.  All the use cases are already covered by `ItemRibKind` and `AssocItemRibKind` which have more precise semantics.

…nxiyn

Extend comma suggestion to cases where fields arent missing

Fixes rust-lang#100300

InferCtxt tainted_by_errors_flag should be Option<ErrorGuaranteed>

Fixes rust-lang#100321.
Use Cell<Option<ErrorGuaranteed>> to guarantee that we emit an error when that flag is set.

… r=davidtwco

Migrate `rustc_plugin_impl` to `SessionDiagnostic`

Migration of the `rustc_plugin_impl` crate.
~Draft PR because it is blocked on rust-lang#100694 for `#[fatal(...)]` support~ (this has been merged, and I've changed over to `#[diag(...)]` now too), but I would also like to know if what I did with `LoadPluginError` is okay, because all it does is display the error message from `libloading` ([See conversation on zulip](https://rust-lang.zulipchat.com/#narrow/stream/147480-t-compiler.2Fwg-diagnostics/topic/.23100717.20diagnostic.20translation/near/294327843)). This crate is apparently for a deprecated feature which is used by servo, so I don't know how much this matters anyway.

…nexen

net listen backlog update, follow-up from rust-lang#97963.

FreeBSD and using system limit instead for others.

…fee1-dead

Fix rustc_parse_format precision & width spans

When a `precision`/`width` was `CountIsName - {:name$}` or `CountIs - {:10}` the `precision_span`/`width_span` was set to `None`

For `width` the name span in `CountIsName(_, name_span)` had its `.start` off by one

r? ``@fee1-dead`` / cc ``@PrestonFrom`` since this is similar to rust-lang#99987

…=davidtwco

Refactor query modifier parsing

Reduce redundancy and improve error spans.

…ylan-DPC

Fix typo in UnreachableProp

r? ``@Dylan-DPC``

…ovement, r=petrochenkov

Minor `ast::LitKind` improvements

r? `@petrochenkov`