Change snapshot status error to use generic SnapshotException (#24355)

Changes the snapshot status read exception from the (misleading)
IndexShardRestoreFailedException to the generic SnapshotException

Closes #24225

core/src/main/java/org/elasticsearch/repositories/blobstore/BlobStoreRepository.java

@@ -954,7 +954,7 @@ public BlobStoreIndexShardSnapshot loadSnapshot() {
             try {
                 return indexShardSnapshotFormat(version).read(blobContainer, snapshotId.getUUID());
             } catch (IOException ex) {
-                throw new IndexShardRestoreFailedException(shardId, "failed to read shard snapshot file", ex);
+                throw new SnapshotException(metadata.name(), snapshotId, "failed to read shard snapshot file for " + shardId, ex);
             }
         }