Fix IncludeBuildNumberInPackageVersion for official builds (dotnet#3181)

When doing an official build and setting a AzDO build variable, the variable turns into an environment variable. When MSBuild props/targets files declare a property, if they don't check if the property is already set, the MSBuild props file will override the environment variable. This causes the AzDO build variable to be ignored.

Adding a check if the IncludeBuildNumberInPackageVersion property is already set before setting it in Directory.Build.props.

Merge pull request dotnet#2861 from shauheen/release/v11final

Update release for 0.11

Merge pull request dotnet#2421 from shauheen/release/v10rc2

Update release for 0.10

Merge pull request dotnet#2067 from shauheen/release/v09rc2

Update release for 0.9

Merge pull request dotnet#1817 from shauheen/release/v0.8RC2

Cherry-pick for release 0.8

Merge pull request dotnet#1547 from shauheen/v07

Cherrypick for release 0.7

Merge pull request dotnet#1119 from shauheen/rc307

Cherrypick release notes for 0.6

Merge pull request dotnet#825 from shauheen/v0.5cp

Cherrypick to update release for 0.5

Add release notes for ML.NET 0.4 (dotnet#656)

Merge pull request dotnet#479 from shauheen/v0.3

Cherrypick to update release for V0.3