hub changes for stream/repost with extensions

[moodyjon]

Context: https://github.com/lbryio/lbry-sdk/pull/3706

Not sure that the query for extensions works as well as I would like.

Also I plan to look into some of the options for limiting how many fields, and how deep the indexing of fields within extensions goes: https://www.elastic.co/guide/en/elasticsearch/reference/current/mapping-settings-limit.html

[moodyjon]

The point of commit https://github.com/lbryio/hub/pull/113/commits/5b1d4bff5c7c57b8613a147fc4d2a89bb9e0d4cb

Is to cut off indexing of all the nested things inside extensions. The fields which are “runtime” can be queried, but not as time-efficiently as others. So you can find extension “cad” quickly because they are indexed, but query on fields like “cad.foo” are evaluated more slowly.