Today we log a "deleting snapshots [...] from repository [...]" message at INFO level [almost the first thing](https://github.com/elastic/elasticsearch/blob/dfaec0dbf0c8a0ba2912381334019725848f1f5a/server/src/main/java/org/elasticsearch/snapshots/SnapshotsService.java#L1886-L1888) when we start the deletion. However, the requested snapshots may not exist or they may be wildcards to be matched against actual snapshots. In these cases, the log message is either misleading or insuffiicent. Instead we should log the message after we have successfully added the delete to the cluster state similar to how the [logging works for snapshot creation](https://github.com/elastic/elasticsearch/blob/f77c16b78bab5e9f3ee24974aeba408e254e8c94/server/src/main/java/org/elasticsearch/snapshots/SnapshotsService.java#L3804).
server/src/main/java/org/elasticsearch/snapshots/SnapshotsService.java
* Returns the data streams that are currently being snapshotted (with partial == false) and that are contained in the
     * indices-to-check set.
     */
    public static Set<String> snapshottingDataStreams(final ClusterState currentState, final Set<String> dataStreamsToCheck) {
        Map<String, DataStream> dataStreams = currentState.metadata().dataStreams();
        return SnapshotsInProgress.get(currentState)
            .asStream()
            .filter(e -> e.partial() == false)
            .flatMap(e -> e.dataStreams().stream())
            .filter(ds -> dataStreams.containsKey(ds) && dataStreamsToCheck.contains(ds))
            .collect(Collectors.toSet());
    }
    /**
     * Returns the indices that are currently being snapshotted (with partial == false) and that are contained in the indices-to-check set.
     */
    public static Set<Index> snapshottingIndices(final ClusterState currentState, final Set<Index> indicesToCheck) {
        final Set<Index> indices = new HashSet<>();
        for (List<SnapshotsInProgress.Entry> snapshotsInRepo : SnapshotsInProgress.get(currentState).entriesByRepo()) {
            for (final SnapshotsInProgress.Entry entry : snapshotsInRepo) {
                if (entry.partial() == false && entry.isClone() == false) {
                    for (String indexName : entry.indices().keySet()) {
                        IndexMetadata indexMetadata = currentState.metadata().index(indexName);
                        if (indexMetadata != null && indicesToCheck.contains(indexMetadata.getIndex())) {
                            indices.add(indexMetadata.getIndex());
                        }
                    }
                }
            }
        }
        return indices;