https://github.com/elastic/elasticsearch/pull/97304 removes several places that might do an expensive rebuild of the cluster state via `getStateForMasterService`. There's one other call we should be able to remove, in `JoinValidationService`, but it's a little tricky since we rely on seeing the last-accepted state for the cluster UUID validation, and it's not obviously ok to expose the last-accepted state without the no-master block.

This is a fairly minor issue because we do not do this join validation during elections, only if we're the elected master, and in that case `getStateForMasterService` is cheap. But that's not guaranteed, and we should strengthen this to avoid the that expensive step whenever possible.
server/src/main/java/org/elasticsearch/cluster/coordination/Coordinator.java
return nodes;
    }
    /**
     * Get the last-accepted state, adding a no-master block and removing the master node ID if we are not currently the master. This is the
     * state that the master service uses as input to the cluster state update computation. Note that it's quite expensive to adjust blocks
     * in a large cluster state, so avoid using this where possible.
     */
    ClusterState getStateForMasterService() {
        synchronized (mutex) {
            
            
            final ClusterState clusterState = coordinationState.get().getLastAcceptedState();
            assert clusterState.nodes().getLocalNode() != null;
            if (mode != Mode.LEADER || clusterState.term() != getCurrentTerm()) {
                
                return clusterStateWithNoMasterBlock(clusterState);
            }
            return clusterState;
        }
    }
    /**
     * Add a no-master block and remove the master node ID from the given cluster state. Note that it's quite expensive to add blocks in a
     * large cluster state, so avoid using this where possible.
     */
    private ClusterState clusterStateWithNoMasterBlock(ClusterState clusterState) {
        if (clusterState.nodes().getMasterNodeId() != null) {
            
            assert clusterState.blocks().hasGlobalBlockWithId(NO_MASTER_BLOCK_ID) == false
                : "NO_MASTER_BLOCK should only be added by Coordinator";
            final ClusterBlocks clusterBlocks = ClusterBlocks.builder()