Rollup merge of #137096 - ehuss:stabilize-doctest-xcompile, r=fmease

Stabilize flags for doctest cross compilation

This makes the following changes in preparation for supporting doctest cross-compiling in cargo:

- Renames `--runtool` and `--runtool-arg` to `--test-runtool` and `--test-runtool-arg` to maintain consistency with other `--test-*` arguments.
- Stabilizes the `--test-runtool` and `--test-runtool-arg`. These are needed in order to support cargo's `target.runner` option which specifies a runner to execute a cross-compiled doctest (for example, qemu).
- Stabilizes the `--enable-per-target-ignores` flag by removing it and making it unconditionally enabled. This makes it possible to disable a doctest on a per-target basis, which I think will be helpful for rolling out this feature.

These changes were suggested in https://rust-lang.zulipchat.com/#narrow/channel/266220-t-rustdoc/topic/stabilizing.20doctest.20xcompile/near/409281127

The intent is to stabilize the doctest-xcompile feature in cargo. This will help ensure that for projects that do cross-compile testing that their doctests are also covered. Currently there is a somewhat surprising behavior that they are ignored.

Closes https://github.com/rust-lang/rust/issues/64245

try-job: x86_64-msvc-1

src/librustdoc/passes/calculate_doc_coverage.rs

@@ -212,7 +212,7 @@ impl DocVisitor<'_> for CoverageCalculator<'_, '_> {
                 let has_docs = !i.attrs.doc_strings.is_empty();
                 let mut tests = Tests { found_tests: 0 };
 
-                find_testable_code(&i.doc_value(), &mut tests, ErrorCodes::No, false, None);
+                find_testable_code(&i.doc_value(), &mut tests, ErrorCodes::No, None);
 
                 let has_doc_example = tests.found_tests != 0;
                 let hir_id = DocContext::as_local_hir_id(self.ctx.tcx, i.item_id).unwrap();