QuickGrid: Adds EmptyContentTemplate

[los93sol]

QuickGrid: Adds EmptyContentTemplate

Description

This PR adds an EmptyContentTemplate component to QuickGrid. When specified by a user they can simply add markup for EmptyContentTemplate and it's child content will be applied to both Virtualize and Paginated views of their table. It also exposes
an internal RenderFragment for EmptyContent so that derivitives of QuickGrid can specify a default implementation easily and still allow users to override. This is a similar model to how ColumnBase deals with the HeaderTemplate.

Fixes #50498

[los93sol]

Just checking if anything is needed on my side to keep this moving?

[ashortland-eqix]

I've created the issue for this one as requested. Hopefully that's enough to get some traction behind this.

[los93sol]

Can someone please review this?

[javiercn]

@los93sol

Thanks for your contributions.

We will be evaluating this PR, #62604 and #62607 for a future release.

As outlined in our contribution guidelines, the team discusses, and triages feature proposals before moving to implementation. This helps us ensure that new features align with our project goals, roadmap and have the necessary community support.

Given where we are in the current release cycle, we'll be evaluating these features for consideration in our next release (post 10.0). We'll review these PRs after we have assessed each proposal according to our triage, planning and prioritization processes.

We want to acknowledge the effort that you have put into creating these PRs, but we hope that you understand that it takes time for any feature to be considered, discussed and prioritized, and that it should fit with the existing roadmap and schedule.