Implement ToolProvider SPI

[sormuras]

This PR implements Java 9's ToolProvider SPI with GoogleJavaFormatToolProvider using google-java-format as the name.

jar --describe-module --file google-java-format-HEAD-SNAPSHOT.jar yields:

No module descriptor found. Derived automatic module.

com.google.googlejavaformat automatic
requires java.base mandated

provides java.util.spi.ToolProvider with com.google.googlejavaformat.java.GoogleJavaFormatToolProvider

contains com.google.googlejavaformat
contains com.google.googlejavaformat.java
contains com.google.googlejavaformat.java.filer
contains com.google.googlejavaformat.java.java14
contains com.google.googlejavaformat.java.javadoc
main-class com.google.googlejavaformat.java.Main

Same new provides line is emitted for the google-java-format-HEAD-SNAPSHOT-all-deps.jar file.

Closes #561

[sormuras]

Btw. this hurts a bit. When will Google upgrade to Jupiter aka JUnit 5️⃣ ? 🙂

[cushon]

I don't have any news on that front :(

[cushon]

Thanks for the PR! This has been merged as part of 2c5d5fd

(There was an issue with the automation that resulted in it getting merged into the same commit as some other changes.)

[sormuras]

Thanks for the heads-up and in the light of that, I'll close the originated issue #561