Suppress false-positives in credential scanning (#4392)

.config/CredScanSuppressions.json

+{
+  "tool": "Credential Scanner",
+  "suppressions": [
+    {
+      "placeholder": "password",
+      "_justification": "This is a fake password used in test code."
+    },
+    {
+      "placeholder": "newpassword",
+      "_justification": "This is a fake password used in test code."
+    },
+    {
+      "placeholder": "AAABAgMEBQYHCAkKCwwNDg+ukCEMDf0yyQ29NYubggE=",
+      "_justification": "This is a fake password hash used in test code."
+    },
+    {
+      "placeholder": "1qaz!QAZ",
+      "_justification": "This is a fake password used in test code."
+    },
+    {
+      "placeholder": "1qaz@WSX",
+      "_justification": "This is a fake password used in test code."
+    }
+  ]
+}