move Sonar UI big text blocks to file resources

[romani]

move big text blocks to files as content to ease editing , avoid violation from MultipleStringLiterals, eventually translate to other languages

[muhlba91]

closing issue as stale.

[rnveach]

@muhlba91 @romani How is this issue stale as we still have code referencing this issue? https://github.com/checkstyle/sonar-checkstyle/search?q=135

[INFO] --- maven-checkstyle-plugin:3.1.2:check (checkstyle-check) @ checkstyle-sonar-plugin ---
[INFO] There are 4 errors reported by Checkstyle 8.35 with https://raw.githubusercontent.com/checkstyle/checkstyle/checkstyle-8.35/config/checkstyle_checks.xml ruleset.
[ERROR] src\main\java\org\sonar\plugins\checkstyle\CheckstylePlugin.java:[38,15] (coding) MultipleStringLiterals: The String "<a href='https://checkstyle.org/config.html'>" appears 2 times in the file.
[ERROR] src\main\java\org\sonar\plugins\checkstyle\CheckstylePlugin.java:[39,15] (coding) MultipleStringLiterals: The String "Checkstyle</a> " appears 2 times in the file.
[ERROR] src\main\java\org\sonar\plugins\checkstyle\CheckstylePlugin.java:[40,15] (coding) MultipleStringLiterals: The String "configuration for more information." appears 2 times in the file.
[ERROR] src\main\java\org\sonar\plugins\checkstyle\CheckstylePlugin.java:[50,15] (coding) MultipleStringLiterals: The String " <a href=\"https://checkstyle.org/config_filters.html" appears 2 times in the file.