add DateTimeOffset to availableStaticMethods (#7517)
add DateTimeOffset to availableStaticMethods (#7517)

Fixes #7504

Context
Add static properties and methods of DateTimeOffset.

Changes Made
Added one line in Constants.cs to add DateTimeOffset to availableStaticMethods.

Testing
Built the bootstrap and tested with the following 'DateTimeOffsetPropFunc.proj' project file:

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
    <Target Name="Test">
        <PropertyGroup>
            <Today>$([System.DateTime]::Now)</Today>
            <Today2>$([System.DateTimeOffset]::Now)</Today2>
        </PropertyGroup>
        <Message Text="DateTime:       $(Today)"/>
        <Message Text="DateTimeOffset: $(Today2)"/>
    </Target>
</Project>
When the project is run with /v:n, the values for DateTime and DateTimeOffset are displayed. The DateTimeOffset value will include the offset from UTC.
rainersigwald/msbuild,sean-gilliam/msbuild,sean-gilliam/msbuild,AndyGerlicher/msbuild,sean-gilliam/msbuild,AndyGerlicher/msbuild,sean-gilliam/msbuild,rainersigwald/msbuild,rainersigwald/msbuild,rainersigwald/msbuild,AndyGerlicher/msbuild,AndyGerlicher/msbuild