Make a proper key_value for the new storage

[Pchelolo]

1. Rename key_value to key_value_old and use it everywhere
2. Adapt the key_value to the new storage - remove unused columns and make a tid a normal column, not a part of a primary key
3. Create new buckets for the new feeds.

cc @wikimedia/services

[d00rman]

This seems a bit too invasive, IMHO. Wouldn't it be better to use the proxy approach we've been using? Which key_value to use could then be specified in the resources section during bucket creation, something along the lines of:

version: 1
valueType: 'json'
backend: 'new'

with the default being backend: 'old'

[Pchelolo]

Then we'd need to specify new/old on very request because we don't really have a space to store whether a particular bucket was created in new/old storage. We can cache that in memory though..

Why do you think it's invasive? it's mostly a mass rename of key_value to key_value_old. We can not do that and name the new bucket key_value_new, but then we'd need to do a mass rename anyways after we switch all to the new bucket.

[Pchelolo]

I've tried switching all the use-cases to the new key_value implementation and the new storage and run the tests and everything looks nice.

[d00rman]

Nit: s/key_value_old/key_value/