Add amendable OverscanCount parameter to the QuickGrid for virtualization.

[MattyLeslie]

QuickGrid: Add OverscanCount Parameter (#49263)

Summary of Changes:
The addition of an OverscanCount parameter to the QuickGrid component. This parameter directly interfaces with the pre-existing OverscanCount property within the Virtualize component during initialization.

Description:
In contrast to the unmodifiable overscan property within the Virtualize component, this enhancement allows for the QuickGrid component to expose a configurable property named OverscanCount. Upon initialization, this property updates the existing OverscanCount attribute within the Virtualize component. The default value remains consistent at "3".

Fixes
#49263 by introducing the OverscanCount property within the QuickGrid component and initializing the Virtualize component with the specified OverscanCount value.

[MattyLeslie]

@MattyLeslie please read the following Contributor License Agreement(CLA). If you agree with the CLA, please reply with the following information.

@dotnet-policy-service agree [company="{your company}"]

Options:

• (default - no company specified) I have sole ownership of intellectual property rights to my Submissions and I am not making Submissions in the course of work for my employer.

@dotnet-policy-service agree

• (when company given) I am making Submissions in the course of work for my employer (or my employer has intellectual property rights in my Submissions by contract or applicable law). I have permission from my employer to make Submissions and enter into this Agreement on behalf of my employer. By signing below, the defined term “You” includes me and my employer.

@dotnet-policy-service agree company="Microsoft"

Contributor License Agreement

@dotnet-policy-service agree company="Retro Rabbit"

[MattyLeslie]

@SteveSandersonMS May I request a review for this please. I may need some feedback on the API changes. Thanks in advance.

[SteveSandersonMS]

@MattyLeslie Certainly, thanks for the prompt.

This looks great. As long as the build passes I think we can accept this as-is.

[MattyLeslie]

@SteveSandersonMS Great to hear, thanks for the review !

[SteveSandersonMS]

Thanks very much!