Add strings for warning when adding a contact is slow
This branch adds UI strings for warning the user when adding a pending contact is taking a long time and giving them a chance to send their link if they've forgotten to do so. I'm imagining the UX working like this:
- If a pending contact was added more than X minutes ago and is in the waiting for connection state, we show an extra message below "Waiting for connection..." that says "Adding this contact is taking longer than usual"
- The extra message is clickable and has a small info/help icon beside it
- Clicking the message/icon opens a dialog
- The dialog's title is "Cannot Connect to Contact" (or maybe "Adding Contact is Slow"?)
- The dialog's text is "Adding this contact is taking longer than usual. Please check that your contact has received your link and added you:"
- The dialog shows the user's link, with copy and share buttons, enabling them to fix the problem
- The dialog has a single button: OK
Part of #1230.