Currently when using `unit` parameter in the `rate` aggregator in time series mode (meaning the `rate` aggregation is defined as a child aggregation of `time_series` aggregation) then this parameter is ignored. We should investigate whether this parameter can be supported for computing rate in time series mode.
x-pack/plugin/analytics/src/main/java/org/elasticsearch/xpack/analytics/rate/TimeSeriesRateAggregator.java
protected final ValuesSource.Numeric valuesSource;
    protected DoubleArray startValues;
    protected DoubleArray endValues;
    protected LongArray startTimes;
    protected LongArray endTimes;
    protected DoubleArray resetCompensations;
    private long currentBucket = -1;
    private long currentEndTime = -1;
    private long currentStartTime = -1;
    private double resetCompensation = 0;
    private double currentEndValue = -1;
    private double currentStartValue = -1;
    private int currentTsid = -1;
    
    protected TimeSeriesRateAggregator(
        String name,
        ValuesSourceConfig valuesSourceConfig,
        Rounding.DateTimeUnit rateUnit,
        RateMode rateMode,
        AggregationContext context,
        Aggregator parent,
        Map<String, Object> metadata
    ) throws IOException {