Switch Sync environment to production

[ayoy]

Task/Issue URL: https://app.asana.com/0/0/1205489036222324/f

Description:
This patch switches default server environment for Sync to production and adds environment switcher
to the Debug menu.

Steps to test this PR:

1. Run the app and identify as internal user
2. Enable Sync, verify that requests are being sent to the production endpoint (sync.duckduckgo.com)
3. Go to Debug menu -> Sync Info -> Environment
4. Verify that it shows that Production is active and it offers you to switch to Development
5. Switch to Development
6. Verify that you have been logged out of Sync
7. Enable Sync, verify that requests are being sent to the development endpoint (dev-sync-use.duckduckgo.com)
8. Go to Debug menu -> Sync -> Environment
9. Verify that it shows that Development is active and it offers you to switch to Production
10. Restart the app, verify that you're still on Development environment.
11. Switch back to Production and verify that you've been logged out.

Device Testing:

• iPhone SE (1st Gen)
• iPhone 8
• iPhone X
• iPhone 14 Pro
• iPad

OS Testing:

• iOS 14
• iOS 15
• iOS 16

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Internal references:

Software Engineering Expectations
Technical Design Template

[bwaresiak]

LGTM!