Execute engine enhancement

[terrymanu]

• Use max.connections.size.per.query to control concurrency for database access on CONNECTION_STRICTLY model
• max.connections.size.per.query greater than table routed count, use MEMORY_STRICTLY automatically
• When table routed count more than maximumPoolSize, use CONNECTION_STRICTLY mode automatically
• Check max.connections.size.per.query must less or equal to maximumPoolSize in Sharding-Proxy (Sharding-JDBC cannot check because of connection pool is provided by end user)
• Hide configuration for MEMORY_STRICTLY & CONNECTION_STRICTLY, just use max.connections.size.per.query to switch model smartly
• Reuse connection if not call close
• Handle get connection for dead lock
  • Get connection sync by data source for MEMORY_STRICTLY, because MEMORY_STRICTLY will hold connection until all query finished
  • Get connection async if connection size is 1
• improve get connection performance
  • Get connection sync for XA transaction
  • Get connection sync for local transaction and BASE transaction