Mustache template behaviour tests

Move FiftyOne.Pipeline.JavaScriptBuilderElementTests.csproj to .NET 8.0 (enable Minimal API usage).
Add Access-Control-Allow-Origin: * header to TestHttpServer's responses.
Split up JavaScriptBuilderElementTests class to introduce parent JavaScriptBuilderElementTestsBase.
Add new test class JavaScriptBuilderElementTemplateTests.

🛠️ Build new JSON with JavaScript snippet property.
🛠️ Visit the page.
- 🗒️ Script invokes the snippet code.
❔ Observe POST data when script calls json endpoint. Check the data set by snippet is present.
❔ Check for complete callback by the script.
❔ Check the snippet was called by testing a flag in window.
🛠️ Replace a JSON with another JavaScript snippet property.
🛠️ Add new cookie.
🛠️ Reload the page.
- 🗒️ Script invokes the new snippet code.
- 🗒️ Script might migrate extra cookie to local storage
❔ Observe POST data when script calls json endpoint. Check all 3 data pieces (persisted old + new + extra) are present.
❔ Check for complete callback by the script.
❔ Check the new snippet was called by testing a flag in window.
❔ Check the old snippet was not called again by testing a flag in window.
❔ [Inconclusive] Check no cookies are set.

51Degrees / pipeline-dotnet