Auto merge of #101138 - Rejyr:diagnostic-migration-rustc-lint-pt2, r=davidtwco

Migrate `rustc_lint` lint diagnostics

Part 2 of [Migrate `rustc_lint` errors to `SessionDiagnostic`](rust-lang/rust#100776)

r? `@davidtwco`

# TODO
- [x] Refactor some lints manually implementing `DecorateLint` to use `Option<Subdiagnostic>`.
- [x] Add `#[rustc_lint_diagnostics]` to lint functions in `context.rs`.
- [x] Migrate `hidden_unicode_codepoints.rs`.
- [x] Migrate `UnsafeCode` in `builtin.rs`.
- [x] Migrate the rest of `builtin.rs`.

Author: bors