With the backport of TDigest, the build started failing compiling with Java 20 with the following error:

```
> Task :libs:elasticsearch-tdigest:compileJava FAILED
../elasticsearch/libs/tdigest/src/main/java/org/elasticsearch/tdigest/SortingDigest.java:57: warning: [lossy-conversions] implicit cast from long to int in compound assignment is possibly lossy
            valuesToAddCount += other.size();
                                          ^
error: warnings found and -Werror specified
1 error
1 warning

```
Java 20 is more picky about lossy conversions,

libs/tdigest/src/test/java/org/elasticsearch/tdigest/ScaleFunctionTests.java
assertEquals(clusterCount.get("K_1"), clusterCount.get("K_1_FAST"));
            }
        }
    }
    /**
     * Validates the bounds on the shape of the different scale functions. The basic idea is
     * that diff difference between minimum and maximum values of k in the region where we
     * can have centroids with >1 sample should be small enough to meet the size limit of
     * the digest, but not small enough to degrade accuracy.
     */
    public void testK() {
        for (ScaleFunction k : ScaleFunction.values()) {
            if (k.name().contains("NO_NORM")) {
                continue;
            }
            if (k.name().contains("K_0")) {
                continue;
            }
            for (double compression : new double[] { 50, 100, 200, 500, 1000 }) {
                for (int n : new int[] { 10, 100, 1000, 10000, 100000, 1_000_000, 10_000_000 }) {
                    
                    double norm = k.normalizer(compression, n);
                    for (double q : new double[] { 0.0001, 0.001, 0.01, 0.1, 0.2, 0.5 }) {
                        if (q * n > 1) {
                            assertEquals(
                                String.format(Locale.ROOT, "%s q: %.4f, compression: %.0f, n: %d", k, q, compression, n),
                                k.k(q, compression, n),
                                k.k(q, norm),
                                1e-10
                            );