Make Style nullable

[pictos]

Description of Change

Add the ? symbol to the Style property of controls.

Issues Fixed

Fixes #25227

[dotnet-policy-service]

Hey there @pictos! Thank you so much for your PR! Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[jsuarezruiz]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[StephaneDelcroix]

it feels weird that among all the properties we have, not attributed as nullable, that Style is the only one to fail.

[mattleibow]

I figured it out. We forgot to add the #nullable disable when we moved the style code into the new StyleableElement.

[mattleibow]

/rebase

This was fixed

[mattleibow]

/azp run

[mattleibow]

/azp run

[PureWeen]

/Users/builder/azdo/_work/3/s/src/Controls/src/Core/PublicAPI/net-tizen/PublicAPI.Unshipped.txt(88,1): error RS0017: Symbol 'Microsoft.Maui.Controls.StyleableElement.Style.get -> Microsoft.Maui.Controls.Style!' is part of the declared API, but is either not public or could not be found (https://github.com/dotnet/roslyn-analyzers/blob/main/src/PublicApiAnalyzers/PublicApiAnalyzers.Help.md) [/Users/builder/azdo/_work/3/s/src/Controls/src/Core/Controls.Core.csproj::TargetFramework=net9.0-tizen7.0]

[pictos]

@PureWeen I removed that entry, not sure if I understood how that API file is written, but I believe when there's a ! at the end, it indicates that value is not nullable, so I remove that line, since there's the same symbol declared there, but it's nullable

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

Feedback was addressed