Update ignite to 2.15.0

[wendigo]

Description

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# Ignite connector
* Upgrade JDBC thin driver to 2.15.0

[ebyhr]

Do you know the link to Ignite JDBC driver's release notes? Probably, https://github.com/apache/ignite/blob/master/RELEASE_NOTES.txt?

Also, I would recommend updating the PR descrption.

[wendigo]

@ebyhr I'm not changing TestingIgniteContainer here so the only user-visible changes are constrained to the JDBC thin driver usage:

• Fixed JDBC connection leak with cache.invoke() over write-behind enabled cache.
• Added endpoints discovery feature.
• Added ClientConfiguration.clusterDiscoveryEnabled configuration property.
• Added events listening.
• Added connections balancing (use random open connection for requests instead of default).
• Added configurable logging.
• Fixed the pending requests race on close.