Extension registry: not finding extensions when searching by name

Created by: sqs

Repro: Go to https://sourcegraph.com/extensions?category=All&query=typescript.

Expected: there should be results, one of which is the sourcegraph/typescript extension.

Actual: no results (see screenshot).

This seems to be related to https://github.com/sourcegraph/sourcegraph/issues/22171 because I see the extension if I am in the Programming languages category (https://sourcegraph.com/extensions?category=Programming+languages&query=typescript). Recommended priority of fixing:

1. Make it so that searches in the All category work (it should search across all extensions; currently it is perhaps only searching extensions whose category is All, which means no extensions).
2. Address UX feedback in #22171 (closed) so that the behavior is clear when you have a non-All category selected and run a search. (I think it should probably not default to just searching within a single category, as that can be confusing.)