upgrade to checkstyle 8.18

[romani]

https://checkstyle.org/releasenotes.html#Release_8.18 ,
upgrade version at https://github.com/checkstyle/sonar-checkstyle/edit/master/pom.xml#L88

from release notes:

Disable loading external DTDs by default, create system property to activate it.

not affected, but it better to update all url to "https"

IllegalType: rename "format" property to "illegalAbstractClassNameFormat".

affected. upgrade instruction: remove old instances of Check and create new.

AnnotationLocation: Remove unused tokens.

affected. upgrade instruction: remove old instances of Check and create new.

Command Line arguments should be allow to exclude a file.

not affected.

New: new filter SuppressionXpathSingleFilter.

affected. we need to provide instruction on how to use it.

ArrayTypeStyle: add support for brackets in method definition after parameters.

no affected.

[romani]

@muhlba91 , please let me know if you can help us to migrate plugin to new version of checkstyle and release your fix for latest sonar support.

[romani]

Done and tested by @muhlba91.

[romani]

RFF - https://community.sonarsource.com/t/rff-checkstyle-plugin-4-18/7576

@muhlba91 , in 2 weeks we can do RELEASE post in sonarqube (so jar will appear in marketplace).

Release process is documented at:
https://github.com/checkstyle/sonar-checkstyle/wiki/How-to-make-release please review it an let me know if smth need to be explained.

[muhlba91]

@romani

I have seen that 6. Announcements has not been done since version 4.10 - if the announcements are not done (anymore), we should remove this point in the document.

Point 8.2: where does an announcement have to be posted and how is the format of it? Or does this refer to 8.3 because then I'd fix the numbering?

[romani]

if the announcements are not done (anymore), we should remove this point in the document.

I tired to do this, it is better to do this, but I do not have time.

Point 8.2: where does an announcement have to

I updated wiki page.

[romani]

@beppo-sturmtief , FYI
https://community.sonarsource.com/t/new-release-checkstyle-plugin-4-18/7988