Make create_dir_all_bare an std integration test

Moving `create_dir_all` out of `ui-fulldeps` is complicated by the fact it sets the current directory. This means it can't be a unit test. Instead, move it to its own integration test.

tests/ui-fulldeps/std/create-dir-all-bare.rs

@@ -1,11 +0,0 @@
-// run-pass
-
-use std::env;
-use std::fs;
-use std::path::PathBuf;
-
-fn main() {
-    let path = PathBuf::from(env::var_os("RUST_TEST_TMPDIR").unwrap());
-    env::set_current_dir(&path).unwrap();
-    fs::create_dir_all("create-dir-all-bare").unwrap();
-}