[Cloud] User settings pre GA tweaks

Created by: artemruts

Description

Pre Cloud GA checklist

• "Sync all" options disabled
• Message about private repos coming soon, with link to get notified
• Users can select "Specific public repos" (label is changed to reflect this)
• Only public repos shown in list

Missing UI

• Textarea to let users add other public repos with URL
  Comments from Alex

  Based on timing concerns, Alex recommended delaying implementation until contexts were closer to available. Reason being: it doesn't do anything for users unless they have a context that can use it with (since public repos are already searchable on Sourcegraph). Check in with @novoselrok
• More filter options for selected public repos
  Comments from Alex and Quinn

  Our internal implementation of a repo/code host has no owner abstraction, so it would have been difficult to do here, we could potentially do this by filtering common prefixes clientside. I think the only drop down i implemented was the code host one, as this list is direct from the code host, we have no concept of status here, Quinn Keast what did you have in mind for the status drop down?

Statuses: Synced, Syncing, Error

Notes

Use AllowUserExternalServicePublic user tag (feature toggle) to show repository view (public repos only)/security page/code host connections.