WPB-24858 [iOS] [Messaging] Incorrect link opens when tapping "Learn more" in a new conversation by user

Issue

The "learn more" link in the E2EE system message at the start of the conversation is hardcoded to a Wire support page. Instead it should be configurable. This PR moves the link to the urls.json config file so it can be changed per build.

Testing

Open the app, navigate to the start of a conversation and tap on the "learn more" link about E2EE. Assert it opens the correct link.

Checklist

• Title contains a reference JIRA issue number like [WPB-XXX].
• Description is filled and free of optional paragraphs.
• Adds/updates automated tests.

UI accessibility checklist

If your PR includes UI changes, please utilize this checklist:

• Make sure you use the API for UI elements that support large fonts.
• All colors are taken from WireDesign.ColorTheme or constructed using WireDesign.BaseColorPalette.
• New UI elements have Accessibility strings for VoiceOver.