Tiny supportability nit: today we emit these log messages when adding a write block to an index:

```
[2022-03-22T19:43:26,897][INFO ][o.e.c.m.MetadataIndexStateService] [node_t1] adding block write to indices [[test-blocks/eLkrYpm_S3WNemfWpXrhPA]]
[2022-03-22T19:43:26,933][INFO ][o.e.c.m.MetadataIndexStateService] [node_t1] completed adding block write to indices [test-blocks]
```

This is kind of confusing, a `block write` sounds like we're writing a block of data. It's not clear that `write` is variable (we also say `block read`) or the name of a block setting. I think we should word this as `adding [index.blocks.write] block to indices` instead.
server/src/main/java/org/elasticsearch/cluster/metadata/MetadataIndexStateService.java
closingBlock,
                true,
                parentTaskId
            );
            if (request.ackTimeout() != null) {
                shardRequest.timeout(request.ackTimeout());
            }
            client.executeLocally(
                TransportVerifyShardBeforeCloseAction.TYPE,
                shardRequest,
                listener.delegateFailure((delegate, replicationResponse) -> {
                    final TransportVerifyShardBeforeCloseAction.ShardRequest req = new TransportVerifyShardBeforeCloseAction.ShardRequest(
                        shardId,
                        closingBlock,
                        false,
                        parentTaskId
                    );
                    if (request.ackTimeout() != null) {
                        req.timeout(request.ackTimeout());
                    }
                    client.executeLocally(TransportVerifyShardBeforeCloseAction.TYPE, req, delegate);
                })
            );
        }
    }
    /**
     * Helper class that coordinates with shards to ensure that blocks have been properly applied to all shards using
     * {@link TransportVerifyShardIndexBlockAction}.
     */
    private class WaitForBlocksApplied extends ActionRunnable<Map<Index, AddBlockResult>> {