Rollup merge of #115154 - olanti-p:move-issues-24-08-2023, r=compiler-errors

Move some ui tests to subdirectories

cc #73494
issue-2804 -> `macros/` (there's already the minified `issue-2804-2` there)
issue-17431 -> `structs-enums/struct-rec` and new `structs-enums/enum-rec` (original issue pertains to detection of recursive enums and structs)
issue-29181 and issue-66768 - moved according to the classifier tool

src/tools/tidy/src/ui_tests.rs

@@ -10,8 +10,8 @@ use std::path::{Path, PathBuf};
 
 const ENTRY_LIMIT: usize = 900;
 // FIXME: The following limits should be reduced eventually.
-const ISSUES_ENTRY_LIMIT: usize = 1891;
-const ROOT_ENTRY_LIMIT: usize = 866;
+const ISSUES_ENTRY_LIMIT: usize = 1874;
+const ROOT_ENTRY_LIMIT: usize = 865;
 
 const EXPECTED_TEST_FILE_EXTENSIONS: &[&str] = &[
     "rs",     // test source files