Configure checkstyle and fix checkstyle warnings

[vrogach2020]

Sync plugin config with https://github.com/tarantool/cartridge-java

Run mvn checkstyle:check and fix everything.

[ArtDu]

It's a lot :)

[INFO] There are 433 errors reported by Checkstyle 8.29 with sun_checks.xml ruleset

Also for javadoc mvn clean javadoc:javadoc

100 warnings
[WARNING] Javadoc Warnings
[WARNING] javadoc: warning - The code being documented uses modules but the packages defined in https://docs.oracle.com/javase/8/docs/api/ are in the unnamed module.
[WARNING] javadoc: warning - The code being documented uses modules but the packages defined in https://docs.oracle.com/javase/8/docs/api/ are in the unnamed module.
[WARNING] javadoc: warning - The code being documented uses modules but the packages defined in https://docs.oracle.com/javase/8/docs/api/ are in the unnamed module
.....