[browser] Override boot config only when the content changes

[maraf]

• Include ArtifactWriter in Wasm SDK tasks.
• Use it when generating boot config to skip file write if the file is the same

PS samples WasmBuildBootIncremental> dotnet build .\BlazorWasm\ -bl -question
Restore complete (0.4s)
    info NETSDK1057: You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy
  BlazorWasm succeeded (1.3s) → BlazorWasm\bin\Debug\net10.0\wwwroot

Build succeeded in 2.2s

Fixes dotnet/aspnetcore#63207

[Copilot]

Pull Request Overview

This PR optimizes WebAssembly build performance by preventing unnecessary file writes to the boot configuration. It includes the ArtifactWriter utility from the .NET SDK and uses it to only write the boot config file when its content has actually changed, enabling incremental builds in Blazor WebAssembly projects.

Key changes:

• Include ArtifactWriter utility class in the WASM app builder tasks
• Replace direct file write with hash-based change detection for boot config generation

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
WasmAppBuilder.csproj	Adds reference to ArtifactWriter.cs for build optimization
BootJsonBuilderHelper.cs	Replaces File.WriteAllText with ArtifactWriter.PersistFileIfChanged
ArtifactWriter.cs	New utility class that compares file hashes to avoid unnecessary writes