Auto merge of #115865 - RalfJung:mir-mod, r=oli-obk

move things out of mir/mod.rs

This moves a bunch of things out of `mir/mod.rs`:
- all const-related stuff to a new file consts.rs
- all statement/place/operand-related stuff to a new file statement.rs
- all pretty-printing related stuff to pretty.rs

`mod.rs` started out with 3100 lines and ends up with 1600. :)

Also there was some pretty-printing stuff in terminator.rs, that also got moved to pretty.rs, and I reordered things in pretty.rs so that it can be grouped by functionality.

Only the commit "use pretty_print_const_value from MIR constant 'extra' printing" has any behavior changes; it resolves the issue of having a fancy and a very crude pretty-printer for `ConstValue`.

r? `@oli-obk`

Author: bors

clippy_utils/src/consts.rs

@@ -656,7 +656,7 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
 }
 
 pub fn miri_to_const<'tcx>(lcx: &LateContext<'tcx>, result: mir::ConstantKind<'tcx>) -> Option<Constant<'tcx>> {
-    use rustc_middle::mir::interpret::ConstValue;
+    use rustc_middle::mir::ConstValue;
     match result {
         mir::ConstantKind::Val(ConstValue::Scalar(Scalar::Int(int)), _) => match result.ty().kind() {
             ty::Adt(adt_def, _) if adt_def.is_struct() => Some(Constant::Adt(result)),

clippy_utils/src/ty.rs

@@ -13,7 +13,7 @@ use rustc_hir::{Expr, FnDecl, LangItem, TyKind, Unsafety};
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_lint::LateContext;
-use rustc_middle::mir::interpret::{ConstValue, Scalar};
+use rustc_middle::mir::{ConstValue, interpret::Scalar};
 use rustc_middle::traits::EvaluationResult;
 use rustc_middle::ty::layout::ValidityRequirement;
 use rustc_middle::ty::{