Detect all file diff types for eng/common changes (#1626)

Fixes https://github.com/Azure/azure-sdk-tools/issues/5882

We need to set the difffilter to empty instead of the default of exclude deleted files when we are trying to verify there are no changes under eng/common.

See test PR https://github.com/Azure/azure-sdk-for-python/pull/32348 which demonstrates us not detecting a deleted file under eng/common. I'll use that same test PR to verify this now catches that issue.

Co-authored-by: Wes Haggard <weshaggard@users.noreply.github.com>

eng/common/pipelines/templates/steps/eng-common-workflow-enforcer.yml

@@ -11,7 +11,7 @@ steps:
 
         if ((!"$(System.PullRequest.SourceBranch)".StartsWith("sync-eng/common")) -and "$(System.PullRequest.TargetBranch)" -match "^(refs/heads/)?$(DefaultBranch)$")
         {
-          $filesInCommonDir  = & "eng/common/scripts/get-changedfiles.ps1" -DiffPath 'eng/common/*'
+          $filesInCommonDir  = & "eng/common/scripts/get-changedfiles.ps1" -DiffPath 'eng/common/*' -DiffFilterType ""
           if (($LASTEXITCODE -eq 0) -and ($filesInCommonDir.Count -gt 0))
           {
             Write-Host "##vso[task.LogIssue type=error;]Changes to files under 'eng/common' directory should not be made in this Repo`n${filesInCommonDir}"
@@ -21,7 +21,7 @@ steps:
         }
         if ((!"$(System.PullRequest.SourceBranch)".StartsWith("sync-.github/workflows")) -and "$(System.PullRequest.TargetBranch)" -match "^(refs/heads/)?$(DefaultBranch)$")
         {
-          $filesInCommonDir  = & "eng/common/scripts/get-changedfiles.ps1" -DiffPath '.github/workflows/*'
+          $filesInCommonDir  = & "eng/common/scripts/get-changedfiles.ps1" -DiffPath '.github/workflows/*' -DiffFilterType ""
           if (($LASTEXITCODE -eq 0) -and ($filesInCommonDir.Count -gt 0))
           {
             Write-Host "##vso[task.LogIssue type=error;]Changes to files under '.github/workflows' directory should not be made in this Repo`n${filesInCommonDir}"
@@ -30,4 +30,4 @@ steps:
           }
         }
       displayName: Prevent changes to eng/common and .github/workflows outside of azure-sdk-tools repo
-      condition: and(succeeded(), ne(variables['Skip.EngCommonWorkflowEnforcer'], 'true'), not(endsWith(variables['Build.Repository.Name'], '-pr')))
+      condition: and(succeeded(), ne(variables['Skip.EngCommonWorkflowEnforcer'], 'true'), not(endsWith(variables['Build.Repository.Name'], '-pr')))