Unistore : Ensure Watch works in HA mode (#94120)

* Revert "Revert "Unistore : Ensure Watch works in HA mode." (#94097)"

This reverts commit 7c3fc2f261.

* make previous_resource_version nullable

* handle nil case

pkg/storage/unified/sql/data/resource_insert.sql

@@ -7,6 +7,7 @@ INSERT INTO {{ .Ident "resource" }}
         {{ .Ident "namespace" }},
         {{ .Ident "name" }},
 
+        {{ .Ident "previous_resource_version" }},
         {{ .Ident "value" }},
         {{ .Ident "action" }}
     )
@@ -17,6 +18,7 @@ INSERT INTO {{ .Ident "resource" }}
         {{ .Arg .WriteEvent.Key.Namespace }},
         {{ .Arg .WriteEvent.Key.Name }},
 
+        {{ .Arg .WriteEvent.PreviousRV }},
         {{ .Arg .WriteEvent.Value }},
         {{ .Arg .WriteEvent.Type }}
     )