Rollup merge of rust-lang#154018 - cyrgani:kindck-tests, r=jieyouxu

simplify and remove `tests/ui/kindck` and related tests

kindck does not exist anymore since a long time now. This PR merges and deletes several redundant tests in that directory, reformats the rest and moves it to `ui/traits`.

Author: JonathanBrouwer

tests/ui/README.md

@@ -778,10 +778,6 @@ These tests revolve around the `--json` compiler flag. See [JSON Output](https:/
 
 Tests exercising keywords, such as attempting to use them as identifiers when not contextual keywords.
 
-## `tests/ui/kindck/`
-
-**FIXME**: `kindck` is no longer a thing, these tests probably need to be audited and rehomed.
-
 ## `tests/ui/label/`
 
 Exercises block and loop `'label`s.