Add Aggregation profiling initially only be for the shard phases (i.e. the reduce phase will not be profiled in this change)
This change refactors the query profiling class to extract abstract classes where it is useful for other profiler types to share code.
It presented as listeners never being called if you refresh at the same
time as the listener is added. It was caught rarely by
testConcurrentRefresh. mostly this is removing code and adding a comment:
```
Note that it is not safe for us to abort early if we haven't advanced the
position here because we set and read lastRefreshedLocation outside of a
synchronized block. We do that so that waiting for a refresh that has
already passed is just a volatile read but the cost is that any check
whether or not we've advanced the position will introduce a race between
adding the listener and the position check. We could work around this by
moving this assignment into the synchronized block below and double
checking lastRefreshedLocation in addOrNotify's synchronized block but
that doesn't seem worth it given that we already skip this process early
if there aren't any listeners to iterate.
```
Sniffer now requires a HostsSniffer instance as a constructor argument, HostsSniffer has its won Builder helper. Also synchronized accesses to scheduledExecutorService in SnifferTask.
This commit addresses a performance issue in
IndicesClusterStateService#applyDeletedShards. Namely, the current
implementation is O(number of indices * number of shards). This is
because of an outer loop over the indices and an inner loop over the
assigned shards, all to check if a shard is in the outer index. Instead,
we can group the shards by index, and then just do a map lookup for each
index.
Testing this on a single-node with 2500 indices, each with 2 shards,
creating an index before this optimization takes 0.90s and after this
optimization takes 0.19s.
Relates #18788
The painless whitelist has a lot of self-checking, in this case, it checks
for missing covariant overrides. It fails on java 9, because LocalDate.getEra()
now returns IsoEra instead of Era: https://bugs.openjdk.java.net/browse/JDK-8072746
To our checker, it thinks we were lazy with whitelisting :)
This means painless works on java 9 again
The database files have been doubled in size compared to the previous files being used.
For this reason the database files are now gzip compressed, which required using
`GZIPInputStream` when loading database files.
