Sync eng/common directory with azure-sdk-tools for PR 3480 (#3806)

eng/common/pipelines/templates/steps/validate-filename.yml

@@ -0,0 +1,18 @@
+parameters:
+  WorkingDirectory: '$(System.DefaultWorkingDirectory)'
+steps:
+  - pwsh: |
+      $differByCaseFiles = git ls-files | Group-Object | Where-Object { $_.Count -gt 1 } 
+
+      if ($differByCaseFiles) 
+      {
+        foreach ($fileGroup in $differByCaseFiles) {
+          Write-Host "Duplicated Files: "
+          Write-Host "[ $($fileGroup.Group) ]"
+        }
+        Write-Host "Do NOT name the files which only differ in case. Please check above files."
+        exit 1
+      }
+      Write-Host "There are no file names that only differ in case."
+    displayName: Check file case duplicates
+    workingDirectory: ${{ parameters.WorkingDirectory }}