【WIP】Add maven-checkstyle-plugin to check code style

[zhaoyuguang]

Describe what this PR does / why we need it

Add maven-checkstyle-plugin to check code style
My local repo test: zhaoyuguang#2

Does this pull request fix one issue?

#935

[fangjian0423]

It seems don't refer https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/spring-cloud-dependencies-parent/eclipse-code-formatter.xml.

[zhaoyuguang]

It seems don't refer https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/spring-cloud-dependencies-parent/eclipse-code-formatter.xml.

Yes, At the moment, I just want to make mvn checkstyle work. There is a useless import in our code, but it seems that CI has passed.

[zhaoyuguang]

@fangjian0423 Hi, I can't find a correct way to finish this, such as
<setting id="org.eclipse.jdt.core.formatter.insert_space_after_ellipsis" value="insert"/>
at https://checkstyle.sourceforge.io/config_whitespace.html#NoWhitespaceAfter, there has no rule for insert_space_after_ellipsis

https://stackoverflow.com/questions/57974305/maven-checkstyle-plugin-can-use-code-format-file-directly

[fangjian0423]

resolved.