An incomplete shard snapshot will prevent a shard from moving away from a node (see `SnapshotInProgressAllocationDecider`). That means that when a shard snapshot completes it may become possible to perform some shard movements that previously were not possible, so we should trigger a reroute to start those movements. AFAICT we do not trigger such a reroute today.
test/framework/src/main/java/org/elasticsearch/test/ESTestCase.java
"HST",
            "IET",
            "IST",
            "JST",
            "MIT",
            "MST",
            "NET",
            "NST",
            "PLT",
            "PNT",
            "PRT",
            "PST",
            "SST",
            "VST"
        );
        Predicate<String> unsupportedZoneIdsPredicate = tz -> tz.startsWith("System/") || tz.equals("Eire");
        Predicate<String> unsupportedTZIdsPredicate = unsupportedJodaTZIds::contains;
        JAVA_TIMEZONE_IDS = Arrays.stream(TimeZone.getAvailableIDs())
            .filter(unsupportedTZIdsPredicate.negate())
            .filter(unsupportedZoneIdsPredicate.negate())
            .sorted()
            .toList();
        JAVA_ZONE_IDS = ZoneId.getAvailableZoneIds().stream().filter(unsupportedZoneIdsPredicate.negate()).sorted().toList();
    }
    @SuppressForbidden(reason = "force log4j and netty sysprops")
    private static void setTestSysProps() {
        System.setProperty("log4j.shutdownHookEnabled", "false");
        System.setProperty("log4j2.disable.jmx", "true");
        
        System.setProperty("io.netty.leakDetection.level", "paranoid");