Allow asynchronously cleanup journal

For the cases when we need to remove a large journal we could benefit from using the async execution provided by delete-by-query methods

Usage example

rake chewy:journal:clean -- --wait_for_completion=false --requests_per_second=10 --scroll_size=5000

Before submitting the PR make sure the following are checked:

[x] The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
[x] Wrote good commit messages.
[x] Commit message starts with [Fix #issue-number] (if the related issue exists).
[x] Feature branch is up-to-date with master (if not - rebase it).
[x] Squashed related commits together.
[x] Added tests.
[x] Added an entry to the changelog if the new code introduces user-observable changes. See changelog entry format for details.

toptal / chewy