Move crates_io_* crates into crates/ dir

[Rustin170506]

Currently, we have numerous files in the crates.io project's root. I suggest moving these individual crates into a sub-directory to reduce the length of the file list in the IDE's explorer.

If it is acceptable I am willing to update it.

[Turbo87]

yeah, I had similar thoughts lately. I guess the main crates_io package would need to stay top-level (unless we adjust the Heroku buildpack accordingly), but the other can probably be moved. The smoke test workflow might also have to be adjusted for the new location.

[Rustin170506]

Thanks for your reply! I will give it a shot.