Added "propr" snippet for required properties

[victor-pogor]

closes #75128

I have checked what modifiers are allowed and limited the propr snippet to the valid cases:

class C
{
    private required int Prop1 { get; set; } // Not valid
    protected required int Prop2 { get; set; } // Not valid
    internal required int Prop3 { get; set; } // OK
    private protected required int Prop4 { get; set; } // Not valid
    protected internal required int Prop5 { get; set; } // OK
    public required int Prop6 { get; set; } // OK
}

interface I
{
    required int Prop { get; set; } // Not valid
}

propr.mp4

[DoctorKrolic]

LGTM. My opinion doesn't count really, but I expect a lot less feedback from the team member now. @victor-pogor You may resolve all leftover feedback items from me. Thanks for great work!

[DoctorKrolic]

@akhera99 PTAL

[akhera99]

Looks good, thank you @victor-pogor for the contribution and @DoctorKrolic for reviewing!