Use java source version for Google Format checks

[laurentgo]

Several spotless check actually use google-java-format under the hoods. When those checks are run from a JDK 17 environment but files are actually targeting Java 8 or Java 11, and also contains some reserved identifiers like yield, those checks would fail because files cannot be parsed (not because they are not conformant).

In general checks should use the version of the language used to compile those files, not the one used to run the plugin, so adding an option to either detect the version or allow the user to specify it would solve the issue.

[laurentgo]

As it turns out, it seems google-java-format itself does not provide such an option. I created a ticket specifically for this project: google/google-java-format#975