[tests] Add manifest timestamp checks to WindowsTest.

[rolfbjarne]

There are random test failures in this test:

Remote .NET tests/Xamarin.Tests.WindowsTest.BundleStructureWithRemoteMac(iOS,"ios-arm64",All,"Debug"): Failed: The target '_CompileAppManifest' was unexpectedly executed (_CompileAppManifest Rebuild 1)

Add more asserts to this test to try to track down what's happening.

[Copilot]

Pull request overview

Adds additional assertions to the Windows remote build BundleStructureWithRemoteMac test to help diagnose sporadic _CompileAppManifest incrementality failures by tracking manifest-related file state across rebuilds.

Changes:

• Introduce helpers to snapshot a file’s last-write timestamp (UTC) and contents, and assert they remain unchanged.
• Capture initial state for AppManifest.plist, _CompileAppManifest.inputs, and shared-dotnet.plist, with a couple of sanity checks on initial build.
• Assert those files remain unchanged across three subsequent rebuilds (after touching code, deleting bin, and a no-op rebuild).

[vs-mobiletools-engineering-service2]

✅ [CI Build #4867e79] Build passed (Build packages) ✅

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Hash: 4867e79bece279d788cbd608d024f194c06c8357 [PR build]

[vs-mobiletools-engineering-service2]

✅ [PR Build #4867e79] Build passed (Detect API changes) ✅

Pipeline on Agent
Hash: 4867e79bece279d788cbd608d024f194c06c8357 [PR build]

[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: 4867e79bece279d788cbd608d024f194c06c8357 [PR build]

[vs-mobiletools-engineering-service2]

✅ [CI Build #4867e79] Build passed (Build macOS tests) ✅

Pipeline on Agent
Hash: 4867e79bece279d788cbd608d024f194c06c8357 [PR build]

[vs-mobiletools-engineering-service2]

🚀 [CI Build #4867e79] Test results 🚀

Test results

✅ All tests passed on VSTS: test results.

🎉 All 156 tests passed 🎉

Tests counts

✅ cecil: All 1 tests passed. [attempt 2] Html Report (VSDrops) Download
✅ dotnettests (iOS): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (MacCatalyst): All 1 tests passed. [attempt 2] Html Report (VSDrops) Download
✅ dotnettests (macOS): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (Multiple platforms): All 1 tests passed. [attempt 4] Html Report (VSDrops) Download
✅ dotnettests (tvOS): All 1 tests passed. [attempt 2] Html Report (VSDrops) Download
✅ framework: All 2 tests passed. [attempt 2] Html Report (VSDrops) Download
✅ fsharp: All 4 tests passed. [attempt 2] 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. [attempt 2] Html Report (VSDrops) Download
✅ linker: All 44 tests passed. [attempt 4] Html Report (VSDrops) Download
✅ monotouch (iOS): All 11 tests passed. [attempt 7] Html Report (VSDrops) Download
✅ monotouch (MacCatalyst): All 15 tests passed. [attempt 2] 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: 4867e79bece279d788cbd608d024f194c06c8357 [PR build]