DDC-2828: [GH-865] Delay foreign keys generation after tables hydration in SchemaTool

[doctrinebot]

Jira issue originally created by user @doctrinebot:

This issue is created automatically through a Github pull request on behalf of dunglas:

Url: #865

Message:

MySQL allows foreign keys only between tables using the InnoDB engine (MyISAM, memory and other engines don't support foreign keys).
This PR delay foreign keys generation after the hydration of all Table objects. It enables DBAL to check tables engines before adding foreign keys.

[doctrinebot]

Comment created by @doctrinebot:

A related Github Pull-Request [GH-865] was closed:
#865

[doctrinebot]

Issue was closed with resolution "Invalid"