Remove InternalsVisibleTo for Toolkit

[jfversluis]

Earlier attempt: #28994 then reverted in: #29321

To provide a transition path and not make this a breaking change immediately we will:

1. Make the types we need for the Toolkit public (Make internal types used by MAUI Toolkit public #29443)
2. Then remove InternalsVisibleTo after we have released .NET 10 and there is a compatible Toolkit version, this can be done in a service release since removing InternalsVisibleTo is not a breaking change.

This issue is there to track number 2. Remove references in these files:

• src\Controls\src\Core\Properties\AssemblyInfo.cs
• src\Controls\src\Xaml\Properties\AssemblyInfo.cs
• src\Core\src\Properties\AssemblyInfo.cs
• src\Essentials\src\AssemblyInfo\AssemblyInfo.shared.cs

When removing InternalsVisibleTo we can also remove src\Controls\src\Core\ILineHeightElementInternal.cs, that is only still there to provide the transition path.