Add Checkstyle and probably Java Format support to the project

[artembilan]

It looks like our own good tool does a decent work on the matter: https://github.com/spring-io/spring-javaformat#gradle.

I would prefer to not have a copy of some classes from other projects like https://github.com/spring-projects/spring-pulsar/blob/main/buildSrc/src/main/java/org/springframework/pulsar/gradle/JavaConventionsPlugin.java and just a plain Gradle config suggested by Spring Java Format mentioned above.