Convert engine/testers to use fs::directory
Convert engine/testers to use fs::directory

Use the new directory abstrction from the utils/fs/directory module
instead of relying on the native opendir(3) family of functions in
engine/testers.

jmmv/kyua,jmmv/kyua,rodrigc/kyua,jmmv/kyua,rodrigc/kyua,rodrigc/kyua,jmmv/kyua,rodrigc/kyua