Try to fix random Swoole crash

• Swoole crash occurs after detecting that pq\Connection is busy in the PqHandle::send method
• Added more verbosity for all operations that call the send method

v2.0.7-beta1: Try to fix random Swoole crash

* Swoole crash occurs after detecting that pq\Connection is busy in the `PqHandle::send` method
* Added more verbosity for all operations that call the `send` method
*

Major fixes

• Concurrency statements fix (fixed an issue when preparing statement failed with "another command is in progress" error)
• Fixed an issue that prevented PqHandle object from being destroyed (excess references to the PqHandle object)

v2.0.6-beta9: PqHandle rewrite to be more AMPHP compatible (and fix concurrency pro…

…blems)

v2.0.6-beta6: PqHandle rewrite to be more AMPHP compatible (and fix concurrency pro…

…blems)

v2.0.6-beta10: PqHandle rewrite to be more AMPHP compatible (and fix concurrency pro…

…blems)

v2.0.6-beta7: Merge pull request #23 from makise-co/feature/pq-concurrent-statement…

…s-fix

Another promise implementation for PqHandle statements

v2.0.6-beta5: Merge pull request #23 from makise-co/feature/pq-concurrent-statement…

…s-fix

Another promise implementation for PqHandle statements

v2.0.6-beta4: Merge pull request #22 from makise-co/feature/pq-concurrent-statement…

…s-fix

Try again to concurrency statement handling

v2.0.6-beta3: Merge pull request #21 from makise-co/feature/pq-concurrent-statement…

Revert AMPHP fix port