[tests] Simplify MonoTouch.Dialog.

[rolfbjarne]

• Remove code we don't use.
• Enable nullability and fix any issues.

[Copilot]

Pull request overview

This PR trims down the tests/common/MonoTouch.Dialog test dependency by removing unused components and enabling C# nullable reference types, updating the remaining code to compile cleanly under nullable analysis.

Changes:

• Enable nullable reference types and treat nullable warnings as errors for MonoTouch.Dialog.
• Remove unused elements/utilities (cache, graphics helpers, custom controls, and several legacy elements).
• Update remaining APIs/implementations with nullable annotations and null-safe logic (events, properties, UI plumbing).

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/common/MonoTouch.Dialog/shared.csproj	Enables nullable and makes nullable diagnostics fatal for this test library.
tests/common/MonoTouch.Dialog/Utilities/Controls.cs	Removes unused types; updates FromResource to return UIImage? and adds null-handling.
tests/common/MonoTouch.Dialog/Elements.cs	Removes unused element types and updates remaining elements for nullable correctness.
tests/common/MonoTouch.Dialog/DialogViewController.cs	Updates search/filter and table source logic for nullable correctness; removes unused search-related APIs.
tests/common/MonoTouch.Dialog/Utilities/LRUCache.cs	Deleted (unused).
tests/common/MonoTouch.Dialog/Utilities/Graphics.cs	Deleted (unused).
tests/common/MonoTouch.Dialog/Utilities/GlassButton.cs	Deleted (unused).
tests/common/MonoTouch.Dialog/OldElements/LoadMoreElement.cs	Deleted (unused).
tests/common/MonoTouch.Dialog/Elements/OwnerDrawnElement.cs	Deleted (unused).
tests/common/MonoTouch.Dialog/Elements/MessageElement.cs	Deleted (unused).
tests/common/MonoTouch.Dialog/Elements/ActivityElement.cs	Deleted (unused).

[vs-mobiletools-engineering-service2]

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[vs-mobiletools-engineering-service2]

✅ API diff for current PR / commit

NET (empty diffs)

• iOS: vsdrops gist ( No breaking changes )
• tvOS: vsdrops gist ( No breaking changes )
• MacCatalyst: vsdrops gist ( No breaking changes )
• macOS: vsdrops gist ( No breaking changes )

✅ API diff vs stable

NET (empty diffs)

• iOS: vsdrops gist ( No breaking changes )
• tvOS: vsdrops gist ( No breaking changes )
• MacCatalyst: vsdrops gist ( No breaking changes )
• macOS: vsdrops gist ( No breaking changes )

ℹ️ Generator diff

Generator Diff: vsdrops (html) vsdrops (raw diff) gist (raw diff) - Please review changes)

Pipeline on Agent
Hash: e7ada3205f5d6c3fbc372c221c7e16d65171a260 [PR build]

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✅ [CI Build #e7ada32] Build passed (Build macOS tests) ✅

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Hash: e7ada3205f5d6c3fbc372c221c7e16d65171a260 [PR build]

[vs-mobiletools-engineering-service2]

🚀 [CI Build #e7ada32] Test results 🚀

Test results

✅ All tests passed on VSTS: test results.

🎉 All 156 tests passed 🎉

Tests counts

✅ cecil: All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (iOS): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (MacCatalyst): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (macOS): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (Multiple platforms): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (tvOS): All 1 tests passed. Html Report (VSDrops) Download
✅ framework: All 2 tests passed. Html Report (VSDrops) Download
✅ fsharp: All 4 tests passed. Html Report (VSDrops) Download
✅ generator: All 5 tests passed. Html Report (VSDrops) Download
✅ interdependent-binding-projects: All 4 tests passed. Html Report (VSDrops) Download
✅ introspection: All 6 tests passed. Html Report (VSDrops) Download
✅ linker: All 44 tests passed. Html Report (VSDrops) Download
✅ monotouch (iOS): All 11 tests passed. Html Report (VSDrops) Download
✅ monotouch (MacCatalyst): All 15 tests passed. Html Report (VSDrops) Download
✅ monotouch (macOS): All 12 tests passed. Html Report (VSDrops) Download
✅ monotouch (tvOS): All 11 tests passed. Html Report (VSDrops) Download
✅ msbuild: All 2 tests passed. Html Report (VSDrops) Download
✅ sharpie: All 1 tests passed. Html Report (VSDrops) Download
✅ windows: All 3 tests passed. Html Report (VSDrops) Download
✅ xcframework: All 4 tests passed. Html Report (VSDrops) Download
✅ xtro: All 1 tests passed. Html Report (VSDrops) Download

macOS tests

✅ Tests on macOS Monterey (12): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Ventura (13): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Sonoma (14): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Sequoia (15): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Tahoe (26): All 5 tests passed. Html Report (VSDrops) Download

Linux Build Verification

✅ Linux build succeeded

Pipeline on Agent
Hash: e7ada3205f5d6c3fbc372c221c7e16d65171a260 [PR build]