Update target framework visibility conditions for VS version compatibility

[Copilot]

Align target framework visibility with VS/MSBuild version support to prevent users from seeing unsupported frameworks in older VS versions.

Changes

• net9.0: Removed MSBuild 17.12.0 version condition (now unconditionally visible)
• net10.0: Added MSBuild 18.0.0+ version condition
• MinimumVisualStudioVersionForUnsupportedTargetFrameworkVersion: Updated from 17.16 to 19.0
• Added comment explaining conditional inclusion rationale

<!-- Before -->
<SupportedNETCoreAppTargetFramework Include=".NETCoreApp,Version=v9.0" 
    Condition="$([MSBuild]::VersionGreaterThanOrEquals($(MSBuildVersion), '17.12.0'))"/>
<SupportedNETCoreAppTargetFramework Include=".NETCoreApp,Version=v10.0" />

<!-- After -->
<SupportedNETCoreAppTargetFramework Include=".NETCoreApp,Version=v9.0" />
<SupportedNETCoreAppTargetFramework Include=".NETCoreApp,Version=v10.0"
    Condition="$([MSBuild]::VersionGreaterThanOrEquals($(MSBuildVersion), '18.0.0'))"/>

This prevents net10.0 from appearing in VS 17.14 (which lacks support) while making it available in VS 18.0.0+.

Original prompt

In this file, we have to make a couple of changes: https://github.com/dotnet/sdk/blob/release/10.0.1xx/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.SupportedTargetFrameworks.props

1. Remove the condition on the net9.0 SupportedNETCoreAppTargetFramework

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