Add Mill AnimalSniffer Plugin (500USD Bounty)

[lihaoyi]

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From the maintainer Li Haoyi: I'm putting a 500USD bounty on this issue, payable by bank transfer on a merged PR implementing this.

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AnimalSniffer is used by many of our third-party example builds: Netty, Mockito, and now Arrow-Kt. We should have official support in Mill for a SpotlessModule to allow usage of Spotless in JavaModule, ScalaModule, and KotlinModule

Should be similar in style of PalantirFormatModule, ScalafmtModule, ErrorProneModule, etc.

[lefou]

Is the AnimalSniffer plugin still relevant for Java 17+? I know it provided support to dedect use of too new API back in the days before javac had the --release option. I used it myself often in combination with retrolambda to write Java 8 lambdas but generate Java 5+ bytecode. But does it provide any value today? E.g. there is no org.codehaus.mojo.signature:java21 artifact on Maven central.