feat: App-specific ApplicationData on Skia

[MartinZikmund]

GitHub Issue (If applicable): related to #6420, closes #8910

Replaces #12314

PR Type

What kind of change does this PR introduce?

What is the current behavior?

What is the new behavior?

Copilot Summary

🤖 Generated by Copilot at b807adc

This pull request adds support for the Skia backend to the SamplesApp project, refactors the rendering and extension logic of the Uno.UI.Composition and Uno.UI.Runtime.Skia.Gtk projects, and aligns the app manifest of the SamplesApp.UWP project with the Uno Platform branding. It also renames, deletes, or updates some files and namespaces to improve the code organization and consistency.

Nope, you didn't get it this time 😂

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Other information

Internal Issue (If applicable):

[MartinZikmund]

@jeromelaban @Youssef1313 The application data path is now correct and user specific on Windows as well as Unix-based platforms, but my concern is with the Temp folder - as Path.GetTempPath() just returns /tmp/ on Linux, which is not really user-specific (as compared to Windows) - https://learn.microsoft.com/en-us/dotnet/api/system.io.path.gettemppath?view=net-7.0&tabs=windows . Also /tmp is potentially very temporary, so it could get cleaned up even while the app is running. Is that acceptable? I provided feature flag to allow overriding the path manually, so the developer is still in control

[Youssef1313]

@MartinZikmund I think /var/tmp would be better on Linux. Tagging @ramezgerges for his view as well.

[ramezgerges]

@MartinZikmund I think /var/tmp would be better on Linux. Tagging @ramezgerges for his view as well.

I'm not sure about the temp directory requirements for Uno specifically, but the vast majority of linux apps/scripts use /tmp directly. Most distros clear /tmp on reboot, and that should be enough for most scenarios. If it isn't, something more persistent like the local folder should probably be used.