Split ApplyDeltaTests into multiple types

[tmat]

Allows tests to run in parallel speeding up the overall test run.

[Copilot]

Pull request overview

This PR refactors test organization by splitting the large ApplyDeltaTests.cs file (1408 lines) into 9 smaller, more focused test files, improving test maintainability and discoverability.

Changes:

• Deletes the monolithic ApplyDeltaTests.cs file
• Creates 9 new focused test files organized by functional area (termination, source updates, project updates, metadata handlers, Razor/Blazor, MAUI, logging, auto-restart, and Aspire)
• Preserves all existing test logic and assertions

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
test/dotnet-watch.Tests/HotReload/ApplyDeltaTests.cs	Deletes the original 1408-line test file
test/dotnet-watch.Tests/HotReload/TerminationTests.cs	New file containing graceful termination tests for Windows (Ctrl+C) and Unix (SIGTERM)
test/dotnet-watch.Tests/HotReload/SourceFileUpdateTests.cs	New file containing tests for source file additions, changes, renames, and dependency updates
test/dotnet-watch.Tests/HotReload/RazorHotReloadTests.cs	New file containing Blazor WebAssembly and Razor component hot reload tests
test/dotnet-watch.Tests/HotReload/ProjectUpdateTests.cs	New file containing tests for project file changes, Directory.Build.props updates, and global usings
test/dotnet-watch.Tests/HotReload/MetadataUpdateHandlerTests.cs	New file containing tests for metadata update handler behavior and exceptions
test/dotnet-watch.Tests/HotReload/MauiHotReloadTests.cs	New file containing MAUI Blazor hot reload tests
test/dotnet-watch.Tests/HotReload/LoggingTests.cs	New file containing binary log generation tests
test/dotnet-watch.Tests/HotReload/AutoRestartTests.cs	New file containing auto-restart tests for rude edits, runtime rude edits, and no-effect edits
test/dotnet-watch.Tests/HotReload/AspireHotReloadTests.cs	New file containing Aspire hot reload tests including build error handling and auto-restart scenarios

[tmat]

@DustinCampbell @MichaelSimons ptal