Refactor >list to be a generic word

This PR aims to make the `>list` conversion word more extensible and consistent with other conversion words, like `>alist`, `>array`, and `>hashtable`. Surprisingly, unlike other conversion words, `>list` doesn't exploit generic dispatch at all - it's hard-coded for lists and sequences using `cond`. So, I moved `>list` from `lists.lazy` to the `lists` vocabulary, made it generic, and added corresponding methods for lists and sequences. These changes don't affect any existing code, since `>list` behaves exactly as before. Both `"lists" test` and `"lists" help-lint` pass successfully.

P.S. I'm sorry for all the trailing whitespaces that have been removed. I have it done automatically by vim.