(chocolatey#2781) Add chocolateyPackageId to env variables

Previously the only env variable to reference a Chocolatey package id
was $env:ChocolateyPackageName. This is inconsistent with the nusepec
file where it is referenced as id.

This commit adds chocolateyPackageId and packageId to the available
environment variables available inside the PowerShell host allowing a
package maintainer to reference the id of a package with the more
idiomatic $env:ChocolateyPackageId.

src/chocolatey/infrastructure.app/services/PowershellService.cs

@@ -435,6 +435,8 @@ public void prepare_powershell_environment(IPackage package, ChocolateyConfigura
 
             Environment.SetEnvironmentVariable("chocolateyPackageName", package.Id);
             Environment.SetEnvironmentVariable("packageName", package.Id);
+            Environment.SetEnvironmentVariable("chocolateyPackageId", package.Id);
+            Environment.SetEnvironmentVariable("packageId", package.Id);
             Environment.SetEnvironmentVariable("chocolateyPackageTitle", package.Title);
             Environment.SetEnvironmentVariable("packageTitle", package.Title);
             Environment.SetEnvironmentVariable("chocolateyPackageVersion", package.Version.to_string());