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
@Override
        public ClusterState execute(ClusterState currentState, List<TaskContext<FinalizeBlocksTask>> taskContexts) throws Exception {
            ClusterState state = currentState;
            for (final var taskContext : taskContexts) {
                try {
                    final var task = taskContext.getTask();
                    final Tuple<ClusterState, List<AddBlockResult>> finalizeResult = finalizeBlock(
                        state,
                        task.blockedIndices,
                        task.verifyResults,
                        task.request.getBlock()
                    );
                    state = finalizeResult.v1();
                    final List<AddBlockResult> indices = finalizeResult.v2();
                    assert indices.size() == task.verifyResults.size();
                    taskContext.success(() -> {
                        final boolean acknowledged = indices.stream().noneMatch(AddBlockResult::hasFailures);
                        task.listener().onResponse(new AddIndexBlockResponse(acknowledged, acknowledged, indices));
                    });
                } catch (Exception e) {