Rollup merge of #125310 - workingjubilee:muck-out-the-test-stables, r=Nilstrieb

Move ~100 tests from tests/ui to subdirs

new dirs for some, the rest in old
sweep tests up before they turn cold
to stop our code from growing mold

Author: matthiaskrgr

src/tools/tidy/src/ui_tests.rs

@@ -16,7 +16,7 @@ const ENTRY_LIMIT: usize = 900;
 // FIXME: The following limits should be reduced eventually.
 
 const ISSUES_ENTRY_LIMIT: usize = 1676;
-const ROOT_ENTRY_LIMIT: usize = 859;
+const ROOT_ENTRY_LIMIT: usize = 757;
 
 const EXPECTED_TEST_FILE_EXTENSIONS: &[&str] = &[
     "rs",     // test source files