Rollup merge of rust-lang#136706 - workingjubilee:finish-up-rustc-abi-updates, r=compiler-errors

compiler: mostly-finish `rustc_abi` updates

This almost-finishes all the updates in the compiler to use `rustc_abi` and removes some of the reexports of `rustc_abi` items in `rustc_target` that were previously available.

r? ```@compiler-errors```

Author: workingjubilee

src/abi.rs

@@ -1,14 +1,15 @@
 #[cfg(feature = "master")]
 use gccjit::FnAttribute;
 use gccjit::{ToLValue, ToRValue, Type};
+use rustc_abi::{Reg, RegKind};
 use rustc_codegen_ssa::traits::{AbiBuilderMethods, BaseTypeCodegenMethods};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::bug;
 use rustc_middle::ty::Ty;
 use rustc_middle::ty::layout::LayoutOf;
 #[cfg(feature = "master")]
 use rustc_session::config;
-use rustc_target::callconv::{ArgAttributes, CastTarget, FnAbi, PassMode, Reg, RegKind};
+use rustc_target::callconv::{ArgAttributes, CastTarget, FnAbi, PassMode};
 
 use crate::builder::Builder;
 use crate::context::CodegenCx;