[Windows] Fixed IsEnabled Property not works on Tabs

[NirmalKumarYuvaraj]

Issue Details

In the Shell, when the Tab.isEnabled property is set to false, the tab should be non-interactive and prevent user interaction. the current behavior allows the tab to be clicked.

Root Cause

In Windows, implementation property for IsEnabled property is not handled.

Description of change

For the Windows platform, a new IsEnabled property was introduced in NavigationViewItemViewModel and registered within NavigationViewItem in the TabbedPageXaml.Windows page. The BaseShellItem.IsEnabled property is now mapped to this newly added property in the view model. Additionally, support was added to handle runtime updates by responding to property-changed events, ensuring the enabled state reflects changes dynamically.

Validated the Behavior in the following Platforms

• Android
• iOS
• mac
• WinUI

Issue fixed

Fixes #5161
Fixes #32996

Screenshots

Before Issue Fix	After Issue Fix
BeforeFix_5161.mp4	AfterFix_5161.mp4

[Redth]

/azp run

[StephaneDelcroix]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[jsuarezruiz]

/rebase

[jsuarezruiz]

/azp run

[StephaneDelcroix]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[rmarinho]

Some little changes, we try not use the private keyword, also we try to use the brackets for making sure we don't missing something that should be in the if statement.

When making the changes please rebase on top of main too.

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[Dhivya-SF4094]

@NirmalKumarYuvaraj looks like this is probably already fixed by #33369 and or #33337 can you confirm?

@jfversluis I have validated this PR against the latest main after the recent iOS changes were merged.
The issue is now fully resolved on the iOS platform by the merged PR, so the iOS-specific changes included in this PR are no longer required.
However, I re-verified the behavior on the Windows platform, and the issue still reproduces there. The Windows fix included in this PR is still necessary and works as expected.