Fix random test failures in TestExchangeClient

Add test pages to output buffer before stating exchange client so client preforms
HTTP request as expected by tests.
Fix state machine in MockExchangeRequestProcessor

Always create mock buffers for requested resources to avoid null pointer exceptions
Consolidate mock buffer code to improve readability
Fix bug in summarizing stats

Stats were not being summarized even if it was requested, if the state
and timeout were not set
Be more aggressive summarizing stats

Remove pipeline stats, since they're unused
Make parsing of taskId parts lazy
Fix IntelliJ warning
Add release notes for 0.84
[maven-release-plugin] prepare release 0.84
[maven-release-plugin] prepare for next development iteration
Replace Murmur3 with Xxhash
Implement hash/equalTo for json type
Removed compareTo method as json type is not orderable
Optimize partition pruning for Hive client

- replace usage of Warehouse.makeSpecFromName with a more efficient implementation
- build filters based on all partition keys, even if they are missing and call
  getPartitionNamesByParts. Use empty string as placeholder for missing filters
- short-circuit parsing partition key values and creating partition objects if
  we can determine the partition doesn't match the predicate
Add 0.85 release notes
[maven-release-plugin] prepare release 0.85
[maven-release-plugin] prepare for next development iteration
Fix tracking of input rows/bytes for JOIN stages

This is a little hacky, since we should really be tracking
just the inputs due to the TableScan operator for any given
stage. However, the current stats rollup system doesn't
support this.
name of WITH query needs to be normalized to be case-insensitive
Add array concat operator

Added array-to-array, element-to-array, and array-to-element concat (||) support
Fix intellij warnings