Rename RecordSink methods in SPI
Add table owner to SPI
Add table creation for Hive
Change default max outstanding splits in Hive to 1000
Bound the total number of threads used by HiveClient
Add toString for HiveOutputTableHandle
Make table owner required

Guava Optional cannot be used in handles because Guava is not part of
the SPI and thus they cannot be serialized due to being in a separate
class loader.
Remove unused class DataSourceType
Fix minor synchronization issue in TaskExecutor

The closed flag was not synchronized but is only used in tests
or when the server is shutdown.
Fix planning of TableCommit to run on coordinator
Fix closing of unpartitioned driver factories
Don't swallow exception when dropping table
Remove support for implicit cross joins

The pre-ANSI join syntax makes it very easy to accidentally perform a
cross join when an inner join was intended, not to mention resulting in
harder to read queries, so we need a way to disable it via configuration.
Add 0.56 release notes
Add note about SPI change
Add note about constant join criteria
Guarantee that semaphore is always released
Fix future exception check
[maven-release-plugin] prepare release 0.56
[maven-release-plugin] prepare for next development iteration