Rollup merge of #85215 - richkadel:ice-fixes-minus-dead-blocks, r=tmandry

coverage bug fixes and some refactoring

This replaces the relevant commits (2 and 3) from PR #85082, and also corrects an error querying for coverageinfo.

1. `coverageinfo` query needs to use the same MIR as codegen

I ran into an error trying to fix dead block coverage and realized the
`coverageinfo` query is getting a different MIR compared to the
codegenned MIR, which can sometimes be a problem during mapgen.

I changed that query to use the `InstandeDef` (which includes the
generic parameter substitutions, prosibly specific to const params)
instead of the `DefId` (without unknown/default const substitutions).

2. Simplified body_span and filtered span code

  Some code cleanup extracted from future (but unfinished) commit to fix
  coverage in attr macro functions.

3. Spanview needs the relevant body_span used for coverage

The coverage body_span doesn't always match the function body_span.

r? ```@tmandry```

compiler/rustc_codegen_ssa/src/mir/coverageinfo.rs

@@ -31,7 +31,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         bx.add_coverage_counter(instance, id, code_region);
                     }
 
-                    let coverageinfo = bx.tcx().coverageinfo(instance.def_id());
+                    let coverageinfo = bx.tcx().coverageinfo(instance.def);
 
                     let fn_name = bx.get_pgo_func_name_var(instance);
                     let hash = bx.const_u64(function_source_hash);