[Blazor] Remove build-time disabling of preloading in tests

[maraf]

Preloading is enabled by placing <ResourcePreloader /> component in the application. We don't need to disable in the tests explicitly during build.

[Copilot]

Pull Request Overview

Removes build-time configuration that explicitly disabled Blazor WebAssembly preloading features in test environments. This change aligns with the new approach where preloading is controlled by adding the <ResourcePreloader /> component to the application rather than being disabled globally at build time.

• Removes WasmPreloadAssets and BlazorCacheBootResources properties set to false
• Simplifies test configuration by removing unnecessary build-time overrides
• Maintains existing behavior through component-based control

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/Components/test/testassets/Directory.Build.props	Removes PropertyGroup blocks that disabled WASM preloading and boot resource caching for test assets
src/Components/benchmarkapps/Wasm.Performance/TestApp/Wasm.Performance.TestApp.csproj	Removes BlazorCacheBootResources=false setting from performance test app
src/Components/WebAssembly/Directory.Build.props	Removes PropertyGroup blocks that disabled preloading features for WebAssembly components