DBAL-666: [GH-414] Enhancement: expose ping() on pingable-connections.

[doctrinebot]

Jira issue originally created by user @doctrinebot:

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

Url: #414

Message:

This PR introduces a new PingableConnection interface and exposes
a ping method on \Doctrine\DBAL\Connection. For drivers where no
ping is supported, a \Doctrine\DBAL\ConnectionException is thrown.

[doctrinebot]

Comment created by @doctrinebot:

A related Github Pull-Request [GH-414] was closed:
#414

[doctrinebot]

Issue was closed with resolution "Fixed"

[github-actions]

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