fix(react-router): fix for useBlocker's stale blockerKey
          #13330
        
          
      
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Fix what causes issue#11430;
useBlockerincorrectly definesblockerKeyas a state value, causing the effect that handles updating the blockerFuntion, when reacting on a newrouterobject, to use a staleblockerKeyvalue that has just been deleted by the cleanup function from the prior effect. This causes the already-deleted key to be re-set into theblockerFunctionsglobal map (inrouter.getBlockerfunction), resulting multiple entries in the map, raising the quoted warning and compromising the router.Since
blockerKeyis meant to track the currentrouterobject (which is reactive) and the latter effect already includesrouterin deps-list,blockerKeycan be defined as an unreactive value wrapped by React Ref object, ensuring the effect uses the newly generated key in the same render cycle that prior effect executes.