chore: create double column container to fix portrait mode - WPB-10140

[caldrian]

WPB-10140 [iOS][iPad] Sidebar - Conversations

Issue

In portrait mode we would like to show the sidebar as overlay, but the conversation list still next to the conversation.
This is currently not supported by UISplitViewController.
This PR creates a custom double column split/container view controller and sets the UISplitViewController's mode to .doubleColumn.

Testing

Rotate the device, use stage manager to resize the app's window.

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Checklist

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

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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.