dotnet pack does not respect Version property in .csproj

# Issue Title

dotnet pack does not respect `Version` property in .csproj

# General

## Steps to reproduce

see also attached sample project [Foo.Bar.zip](https://github.com/dotnet/core/files/4394193/Foo.Bar.zip)

1. Create a new classlib project `dotnet new classlib -n Foo.Bar`
1. Set `1.0.0.0` in your Foo.Bar.csproj file
1. Run `dotnet pack`

## Result

The resulting .nupkg file will be named `Foo.Bar.1.0.0.nupkg`.

## Expected Result

The resulting .nupkg file should be named `Foo.Bar.1.0.0.0.nupkg`.

If I change the `Version` property to `1.0.0.1` the resulting .nupkg file has the expected name `Foo.Bar.1.0.0.1.nupkg`.

## dotnet version and OS info

.NET Core SDK (gemäß "global.json"):
Version: 3.1.103
Commit: 6f74c4a1dd

Laufzeitumgebung:
OS Name: manjaro
OS Version:
OS Platform: Linux
RID: arch-x64
Base Path: /usr/share/dotnet/sdk/3.1.103/

Host (useful for support):
Version: 3.1.3
Commit: 9678feff10

.NET Core SDKs installed:
3.1.103 [/usr/share/dotnet/sdk]

.NET Core runtimes installed:
Microsoft.AspNetCore.App 3.1.3 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 3.1.3 [/usr/share/dotnet/shared/Microsoft.NETCore.App]