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
final Map<Index, ClusterBlock> blockedIndices,
        final Map<Index, AddBlockResult> verifyResult,
        final APIBlock block
    ) {
        final ClusterBlocks.Builder blocks = ClusterBlocks.builder(currentState.blocks());
        final Set<String> effectivelyBlockedIndices = new HashSet<>();
        Map<Index, AddBlockResult> blockingResults = new HashMap<>(verifyResult);
        for (Map.Entry<Index, AddBlockResult> result : verifyResult.entrySet()) {
            final Index index = result.getKey();
            final boolean acknowledged = result.getValue().hasFailures() == false;
            try {
                if (acknowledged == false) {
                    logger.debug("verification of shards before blocking {} failed [{}]", index, result);
                    continue;
                }
                final ClusterBlock tempBlock = blockedIndices.get(index);
                assert tempBlock != null;
                assert tempBlock.uuid() != null;
                final ClusterBlock currentBlock = currentState.blocks().getIndexBlockWithId(index.getName(), tempBlock.id());
                if (currentBlock != null && currentBlock.equals(block.block)) {
                    logger.debug(
                        "verification of shards for {} succeeded, but block finalization already occurred"
                            + " (possibly for another block) [{}]",
                        index,
                        result
                    );
                    continue;
                }
                if (currentBlock == null || currentBlock.equals(tempBlock) == false) {