Extend the left filter functionality to allow searching outside of faceted repos

Created by: macraig

Feedback

Internal feedback submitted by @slimsag Slack thread reference: https://sourcegraph.slack.com/archives/C0W2E592M/p1626375636074200

When I search in the repos input on the search page, I do not find the repos I am expecting to find. I know why this is, but as a user this is really confusing.

I just want it to find the Sourcegraph repository or github org and let me search within that. I do not see a good reason for it to be limited to just repositories in my query at all.

Relates to https://github.com/sourcegraph/sourcegraph/issues/20158