[UI/UX] Rephrase DevicesView Instructions

Change instructions to provide scenario-based help in DevicesView.

Changelog

• Simplified the text displayed when each section is empty
• Adds a dedicated help popup for fixing device discovery issues
• Only include footer help for reconnecting previously connected devices if there are remembered devices

Rationale

People look for help when they can’t figure out how to accomplish a goal. Although users sometimes want a quick reference guide, they’re more likely to seek help with specific tasks. In general, describe control usage in the context of accomplishing a task. https://developer.apple.com/design/human-interface-guidelines/macos/user-interaction/help/#apple-help

We received a question about KDE Connect iOS not being able to discover other devices, and they were able to resolve it by following the instruction listed as the section footer, which is "Configure Devices by IP." Despite the current phrasing accurately identifying why the problem happened, it isn't clear to the users that the instruction is for such a problem.

Additionally, we have feedback on TestFlight that states:

UI/UX modification requests: 4. Shorten the Discoverable Devices warning on the main opening page to this: "No new devices discovered. Please refresh discovery and check if other devices are running KDE connect & are on the same network as this this device." Current warning has some grammatical errors and lengthy text becomes distracting/confusing to user.

Thus, we could mimic examples from the iOS Settings App:

Footer	Popover

Demo

iOS 15

1. All sections are empty, no additional help other than for discovery

2. Has no remembered device

3. Has no discovered and no remembered device

4. Has remembered device, provides additional help about reconnecting remembered devices

5. Help for device discovery

iPad

Help for device discovery on iPad takes only readable width

iOS 14 (difference only)

Footer is displayed as just another row