[WIP] Create draft PR for backporting test changes

[Copilot]

⚠️ This PR cannot be used as-is for the backport

Due to tooling limitations, this PR branch is based on main rather than release/10.0. The changes from PR #123388 are already in main, so they don't appear in this PR's diff.

Recommended action:

Use the backport bot by commenting on PR #123388:

/backport to release/10.0

Or manually cherry-pick:

git checkout release/10.0
git checkout -b backport/pr-123388-to-release-10.0
git cherry-pick ebae78473acc58e90140d58bf87bcc356305244d
# Resolve conflicts: keep net10.0 in csproj files
git push origin backport/pr-123388-to-release-10.0
# Create PR targeting release/10.0

---

Backport template (for the new PR):

Backport of #123388 to release/10.0

/cc @oroztocil

**This change only affects test code and does not impact any shipped code.**

## Description

Backports the rework of `Wasm.Build.Tests.Blazor.AssetCachingTests` from PR #123388. The test was flaky due to relying on reading server logs from stdout. This change replaces the mechanism with an API endpoint exposed by the test server that is used by the test code to retrieve the captured request logs.

## Testing

- Test infrastructure change only
- No product code is modified

## Risk

**None** - This is a test-only change that improves test reliability.

---

Status

• Prepared backport PR description template
• Identified changes needed (from PR Rework and enable Wasm.Build.Tests.Blazor.AssetCachingTests #123388)
• Noted net11.0 → net10.0 adaptation needed
• ⚠️ Cannot complete: PR requires manual creation targeting release/10.0

Original prompt

Create a cherrypicked PR that backports changes from @dotnet/runtime/pull/123388 into the branch release/10.0
Create the PR as draft and tag me when done
Use the template for backport PRs, e.g. see @dotnet/runtime/pull/123762
But since this change is only to tests, keep a very short description saying the change does not impact shipped code

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.