improvement: Publish executable shadowJar for formatter with CLI

[andreweacott]

Configure the palantir-java-format module to publish the shadowJar (fat JAR with all dependencies) as an additional artifact with 'executable' classifier. This enables distributing a self-contained formatter jar alongside the standard library artifacts.

Before this PR

The palantir-java-format Jar artifacts published from CI are not executable, making it hard to use the formatter as a CLI

After this PR

• A shadow Jar is built alongside the default formatter Jar
• The shadow Jar is additionally published to Maven with the 'executable' classifier

Possible downsides?

None I can think of

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💡 Improvements

• Publish executable shadowJar for formatter with CLI (#1464)