Implement _many methods on stores

[strawgate]

Many of the stores use the fallback behavior for bulk operations. The fallback behavior calls put/get/etc in a loop.

Let's identify which stores have bulk apis available and leverage those for _many operations. If they dont have bulk APIs we can leave them alone. If they do have bulk APIs, we should use them, keeping in mind any client-specific bulk behavior like max number of entries, etc.

We do not need new tests for these as the existing tests cover.