Move iOS projects to always use spaces for indentation

[mischreiber]

Platforms Impacted

• iOS
• visionOS
• macOS

Description of changes

We always want spaces for indentation in our iOS projects--let's enforce that at an Xcode project level. Useful for people (like me!) who move between tabs-only and spaces-only projects.

Binary change

n/a -- no impact on build

Verification

Verified that Xcode uses spaces in both the library and demo app projects, even when the global app settings are set to tabs.

Visual Verification

n/a

Pull request checklist

This PR has considered:

• Light and Dark appearances
• iOS supported versions (all major versions greater than or equal current target deployment version)
• VoiceOver and Keyboard Accessibility
• Internationalization and Right to Left layouts
• Different resolutions (1x, 2x, 3x)
• Size classes and window sizes (iPhone vs iPad, notched devices, multitasking, different window sizes, etc)
• iPad Pointer interaction
• SwiftUI consumption (validation or new demo scenarios needed)
• Objective-C exposure (provide it only if needed)

Microsoft Reviewers: Open in CodeFlow

[laminesm]

Should these rules be mirrored for fluent Mac as well?

[mischreiber]

Should these rules be mirrored for fluent Mac as well?

Turns out that the vast majority of Fluent Mac code still uses tabs, rather than spaces. We'll have to think about what to do there before making any commitments.