Implement rustc_public::CrateDef{,Type} for FieldDef

[erickt]

This migrates FieldDef to implement CrateDef and CrateDefType, which matches the other DefId wrappers. This allows access to field info, like the underlying DefId, the name, and any tool attributes on the field.

[rustbot]

This PR changes rustc_public

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

[rustbot]

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[rust-log-analyzer]

The job aarch64-gnu-llvm-21-1 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

---- [ui] tests/ui-fulldeps/rustc_public/check_ty_fold.rs stdout ----

error: test compilation failed although it shouldn't!
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui-fulldeps/rustc_public/check_ty_fold.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2" "--target=aarch64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "-O" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui-fulldeps/rustc_public/check_ty_fold/a" "-A" "internal_features" "-A" "incomplete_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "--edition=2021"
stdout: none
--- stderr -------------------------------
error[E0599]: no method named `ty_with_args` found for reference `&rustc_public::ty::FieldDef` in the current scope
##[error]  --> /checkout/tests/ui-fulldeps/rustc_public/check_ty_fold.rs:52:30
   |
LL |     let field_ty = field_def.ty_with_args(&args);
   |                              ^^^^^^^^^^^^ method not found in `&rustc_public::ty::FieldDef`
   |
   = help: items from traits can only be used if the trait is in scope
help: trait `CrateDefType` which provides `ty_with_args` is implemented but not in scope; perhaps you want to import it
   |
LL + use crate::rustc_public::CrateDefType;