Update buildkite to produce the bundled DBs artifacts during release

[jakubcech]

Description

We'd like to have the release process created additional artifacts that we publish on GitHub. In addition to the .JAR file, we'd like to make sure the release also contains a good spent addresses DB.

Motivation

Less room for leaving out a spent addresses DB when creating a node.

Requirements

• [ ] The IRI Release BuildKite pipeline produces a .zip file.
• [ ] The .zip file contains the .JAR file and the spent addresses DB folder. The exact folder name and structure will be decided in https://github.com/iotaledger/iri/issues/1317

Open questions

• [ ] ? Can the release process run an IXI on one of our nodes? This would ensure it generates the spent addresses DB itself during the release process.

[sadjy]

• Combine spent-addresses-db from other nodes to source node before implementing the above.
• No more .zip file. Upload .jar and .tar of spent-addresses-db separately