[DataGrid] Asynchronous IQueryable based loading enhancements

[miguelhasse]

Pull Request

📖 Description

This pull request provides fixes/enhancements to the DataGrid component:

• Fixed async 'Loading' state flag feedback, making sure data is not refreshed unnecessarily.
• Fixed Virtual mode switch render handling, making sure data is correctly refreshed when deactivated

👩‍💻 Reviewer Notes

A working samples can be seen in the following repository projects:

• AdventureWorks showing dynamic data loading using EntityFrameworkAsyncQueryExecutor in a Blazor Server app
• TripPin showing dynamic data loading using ODataAsyncQueryExecutor in a Blazor WebAssembly app

✅ Checklist

General

• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.

Component-specific

• I have added a new component
• I have added Unit Tests for my new component
• I have modified an existing component
• I have validated the Unit Tests for an existing component

[vnbaaij]

Have you also tested that the DataGrid still functions normally when not using the adapters? Like with the samples in the demo site itself?

I think we need to do that before merging this in. If needed, I can do this.

[miguelhasse]

@vnbaaij I ran all the demo app scenarios for testing. All good!
You can further test using the apps I've provided above :)